Tips for overcoming laziness

Are you sure this is laziness and not clinical depression? If I were in your shoes, I'd get that sorted first. But to answer your question - start using your body. When we fall into a funk like that, even if it isn't clinical depression, it's easy to spiral down the toilet of apathy. Commitments get missed, we feel bad about it, and our down and out feelings sap our motivation still further. Soon we're not doing anything more than feeling sorry for ourselves.

You need a way to upend that karmic cycle. The body provides the most expedient means for doing so.

Once upon a time, there was a monastery in China by the name of Shaolin. In it were a bunch of rather unhealthy, depressive, short-lived monks. It wasn't a very happy place. A fellow by the name of Bodhidharma happened upon them and felt compelled to help them regain their vigor. He taught them a series of exercises that involved stretching and strengthening exercises. Over time, these monks regained their vitality. Not only that, but their meditation improved as well. I think that temple went on to do some other things, but I'm not entirely sure...

All kidding aside, you obviously don't need to become a master martial artist to get the same benefit (though I'd highly recommend tai chi; I can't begin to tell you how much that improved my zazen!). Something as simple as a daily walking practice will help immensely. Meditation is hard. It takes a shocking amount of discipline to sit on your butt and stare at your eyelids for hours at a time. I mean that sincerely. But walking? Just about anyone can do that. Keep at it, day after day. Go out in cold weather, go out in hot weather, go out when it's nice. In time, your ability to motivate yourself will drastically improve. You will be able to take on tasks that seem impossibly burdensome now. I'm also willing to bet that once you really get rolling, you'll be able to sit like a stone!

Setting a small goal for yourself every week might help. For the first month, you could set the goal to sit 5 minutes every week and then gradually increase it. If getting out of bed is difficult, wake up 5 minutes earlier than your current baseline everyday. The Buddha recommended the middle path. Moderation is a virtue.

In the past, I didn’t want to sit everyday, but based on my values I made it a part of my daily routine. Sometimes, other things might matter, but in Eckhardt Tolle’s words, you have to find out what matters absolutely. I agree putting it into practice can be difficult. Find out what you truly value and then remind yourself.

Ruling out health problems is also important as another answer pointed at. Having a good relationship with a primary care physician and going for annual physicals can help. He would most likely recommend a balanced diet and exercise.

When talking about laziness, it's important to distinguish between useful laziness (i.e., inventing the wheel) as opposed to useless laziness. Let's look at the suttas.

Useful laziness (i.e., inaction) would be:

AN8.12:17.3: I teach inaction regarding bad bodily, verbal, and mental conduct,

And useless laziness would be:

AN8.80:1.1: “Mendicants, there are eight grounds for laziness.

You mention getting out of bed to face the day and its demands. This is related to the first ground for laziness:

AN8.80:1.5: ‘I have some work to do. But while doing it my body will get tired. I’d better have a lie down.’
AN8.80:1.6: They lie down, and don’t rouse energy for attaining the unattained, achieving the unachieved, and realizing the unrealized.
AN8.80:1.7: This is the first ground for laziness.

And the Buddha agrees with your "just do it":

AN8.80:10.3: ‘I’ve done some work. While I was working I wasn’t able to focus on the instructions of the Buddhas. I’d better preemptively rouse up energy for attaining the unattained, achieving the unachieved, and realizing the unrealized.’
AN8.80:10.4: They rouse up energy …
AN8.80:10.5: This is the second ground for arousing energy.

The "just do it" approach works well for people who have energy during the day for various pursuits.

NOTE: However, it may also help to see a doctor for a medical diagnosis if a lack of energy pervades all your waking moments. In that case, there may be a medical cause.

Here are my notes, a collection of sutta passages and some commentary on the hindrance of sloth and torpor. https://lucid24.org/sted/5niv/5niv3/index.html

But by far the most useful thing in my decades of meditation practice, in overcoming laziness, sloth and torpor, is doing exercises to strengthen the body, and eating healthily and correctly (not undereating, not overeating). Collection of notes on that here: https://lucid24.org/misc/qigor/index.html

The number one physical exercise I can recommend for laziness, sloth, is "shake and bake" (detailed in article above). Basically, it's the equivalent of doing slow jogging, or easy paced swimming, or doing jump rope without the rope (so one can fully relax and not tense up from fear of tripping). Do at least twenty minutes of that (shake and bake or equivalent cardio), and you'll feel energetic and not lazy, ready to rock (meditate). The benefits of that are amazing, expending only about 10% more energy than a casual walking exercise, it builds up your cardio conditioning (if you do 20-30min everyday) such that you'll then be able to do regular paced jogging easily without panting, stress, pain, or discomfort after a few months.

laziness will be no problem at this point. If you eat unhealthy and don't get enough physical exercise, even if you have the mind of a supermonk and no laziness, your body will still fail you and you'll just be forcing your way through bad meditations because of a malnourished unconditioned body.

Ajahn Brahm wrote the following in his essay entitled "Five Hindrances".

The method to overcome sloth and torpor is written in the quote below i.e. by rousing energy through developing interest.

Sloth and torpor refers to that heaviness of body and dullness of mind which drag one down into disabling inertia and thick depression. The Lord Buddha compared it to being imprisoned in a cramped, dark cell, unable to move freely in the bright sunshine outside. In meditation, it causes weak and intermittent mindfulness which can even lead to falling asleep in meditation without even realising it!

Sloth and torpor is overcome by rousing energy. Energy is always available but few know how to turn on the switch, as it were. Setting a goal, a reasonable goal, is a wise and effective way to generate energy, as is deliberately developing interest in the task at hand. A young child has a natural interest, and consequent energy, because its world is so new. Thus, if one can learn to look at one's life, or one's meditation, with a 'beginner's mind' one can see ever new angles and fresh possibilities which keep one distant from sloth and torpor, alive and energetic. Similarly, one can develop delight in whatever one is doing by training one's perception to see the beautiful in the ordinary, thereby generating the interest which avoids the half-death that is sloth and torpor.

The mind has two main functions, 'doing' and 'knowing'. The way of meditation is to calm the 'doing' to complete tranquillity while maintaining the 'knowing'. Sloth and torpor occur when one carelessly calms both the 'doing' and the 'knowing', unable to distinguish between them.

Sloth and torpor is a common problem which can creep up and smother one slowly. A skillful meditator keeps a sharp look-out for the first signs of sloth and torpor and is thus able to spot its approach and take evasive action before it's too late. Like coming to a fork in a road, one can take that mental path leading away from sloth and torpor. Sloth and torpor is an unpleasant state of body and mind, too stiff to leap into the bliss of Jhana and too blinded to spot any insights. In short, it is a complete waste of precious time.

The advice from SN 9.2 would also be helpful:

Now at that time that mendicant fell asleep during the day’s meditation. The deity haunting that forest had compassion for that mendicant, and wanted what’s best for them. So they approached that mendicant wanting to stir them up, and addressed them in verse:

“Get up, mendicant! Why lie down?
What’s the point in your sleeping?
What slumber can there be for those afflicted,
injured, pierced by an arrow?

You should amplify the faith
that led you to go forth
from the home life to homelessness.
Don’t fall under the sway of slumber.”

SN 9.2