How can I accept losing control of my mind and will?

If you think you aren't helping as much as you wished you should try to see how you could. Even if it would be to go to a doctor, practice ex Medicine Buddha, following your Guru advices.

If you are already doing what you can, as much as it's possible right now, don't worry so much, it's not you fault, things take time to heal and they do change, even if that doesn't you will change the way you deal with it or just forget it's there.

I hope this helps, Blessings

I think you can reflect on the mind's changing being inevitable as old age.

If intellect has knowledge about how mind changes then the course of development will reflect that.

Past conditioning can not be undone and bad mental & physical behaviors will come into play.

One should reflect on conditioning and let wisdom steer as much as possible.

There is essentially nobody commanding the faculties of knowledge & bodily functions. It's nature in development and mind seeks knowledge like roots seek nutriment.

Whatever one sees or thinks about that one gives attention, what is given frequent attention becomes the inclination of the mind.

Executing a complex learned behavior requires strategy, effort and concentration and one can develop these.

Basically i am telling you to develop the recommended lines of reasoning

• old age
• not-self
• impermanence
• death & birth
• appreciation
• defining elements
• appreciation & gladness
• metta & compassion
• equanimity
• on the drawbacks
• on the danger
• on the unattractiveness

When these themes develop into one another by inference then a lot has been done imo. Then they will come to mind often and together directing behavior.

I have sutta excerpts here https://docs.google.com/document/d/1kZxstsAvjhj9Svc47RUKRIyKQMuHMD4adIvr_7pp2uI/edit?usp=drivesdk

Reflection, contemplation and stlling of the mind is what you want to do.

You can also develop kasina meditative states by contemplation or some sort of mindfulness of the body training & stilling of distractive thoughts.

Then one should also learn about hindrances & factors of enlightenment.

If successful in contemplation & stilling of thoughts then one should have little difficulty attaining jhana.

Training like this one will grow equanimous to mind's changes.

Before you aim to lose control of your mind I urge you to read this answer with regards to what Volition (conditioned free will) is.

Unless you are fully liberated don't be too quick to say there is no controller. You are the owner of your volition.

It is not wise to say volition, including all bad volition, is uncontrolled because it offers a free license for unaccountability.

the quote below is from Attakārī Sutta

So, brahmin, when there is the element of endeavoring, endeavoring beings are clearly discerned; of such beings, this is the self-doer, this, the other-doer. I have not, brahmin, seen or heard such a doctrine, such a view as yours. How, indeed, could one — moving forward by himself, moving back by himself — say ‘There is no self-doer, there is no other-doer’?*

Also reads the notes:

Although the Buddha taught that there is no permanent, eternal, immutable, independently-existing core “self” (attā), he also taught that there is “action” or “doing”, and that it is therefore meaningful to speak of one who intends, initiates, sustains and completes actions and deeds, and who is therefore an ethically responsible and culpable being.

-You overcome the fear by paying attention, continuously, on purpose, on a moment by moment basis and you see the experience of the fear not the concept of fear.

-Listen and chant up a loving kindness attitude for temporarily destroying anger or fear(aversion).

Fighting fear makes it grow. Letting go of fear, it will disappear just as it arose. Fear is temporary. Temporary things are not worth clinging to:

MN62:3.2: “Rāhula, you should truly see any kind of form at all—past, future, or present; internal or external; coarse or fine; inferior or superior; far or near: all form—with right understanding: ‘This is not mine, I am not this, this is not my self.’”

Instead of fear, be mindful. If there is fear of transgression, simply relax into mindfulness of ethics:

MN8:12.2: ‘Others will be cruel, but here we will not be cruel.’
MN8:12.5: ‘Others will be unchaste, but here we will not be unchaste.’
MN8:12.10: ‘Others will be covetous, but here we will not be covetous.’
MN8:12.22: ‘Others will be overcome with dullness and drowsiness, but here we will be rid of dullness and drowsiness.’
MN8:12.23: ‘Others will be restless, but here we will not be restless.’
MN8:12.24: ‘Others will have doubts, but here we will have gone beyond doubt.’ ...

Yet while being mindful of ethics, cravings may bother mindfulness. But cravings are temporary. And if they are temporary, then cravings are unsatisfactory. Let go of cravings, thinking:

MN62:3.2: “Rāhula, you should truly see any kind of form at all—past, future, or present; internal or external; coarse or fine; inferior or superior; far or near: all form—with right understanding: ‘This is not mine, I am not this, this is not my self.’”

Ethics belong to us all. They can be ignored but not lost or possessed. So be mindful of ethics with each breath, relaxed and content. Be free of suffering. Be free of fear.

Fear is a reoccurring companion on the spiritual path. It doesn't mean that something has gone wrong. The particular fear that you describe seems fairly common, but fears can come in all sorts of shapes and sizes; all sorts of feelings and thoughts.

How can I overcome this fear?

The overcoming of fear happens when we become curious about it rather than adhering to its demands which generally push the practitioner towards form-based experiences or sensuality - that is the habitual response. This only serves to cover over the those fears and the practitioner loses sight of some critical knowledge. However, approaching fear with curiosity suggests that there is another way to understand those fears. Therefore, fear holds previously unseen knowledge... knowledge about uncertainty and not just the uncertainty of our mental faculties, but the uncertainty of every single second that passes by.

When one consciously choses to look towards those fears, slowly they lose their power over you. One does not need to analyse why they are there rather, just to notice that they are present. You see, fear is like a snotty-nosed child trying to play a sinister melody with a trumpet, but if we don't turn towards its comical absurdity, we perceive fear as something much greater, something that has much more substance; fear then continues as a deep intrapsychic governor giving determinations on how we live our lives.

Fear only perpetuates when there is an applied force. We can recognize those applied forces in our thoughts and if we buy into those thoughts fear quickly takes the upper hand. One common fear is the fear of going crazy.

Is this a fetter? In particular, is it caused or conditioned by belief in self? Are dispositions part of self?

It's not quite a fetter, but a pre-emptive response to the practice as a whole. The fetter model has its quagmires; it's not a solid base for practice, so I wouldn't hold that model too tightly.

The practice uncovers these deep fears and allows us the opportunity to view them in more healthy ways. It's time to start doing that now. This calls upon a certain degree of wisdom, perhaps some faith, and an ability to find some contextual awareness.

In an nutshell, the fear is the anticipation of its own ending, but it can only express this through negative thoughts. It is fearful because what lies beyond our internal conceptual world cannot be conceived by it, by the feelings it generates or by the thoughts it weaves.

The amazing thing is, we fear the loss of control but none of us ever had any control and never will.

How can I accept losing control of my mind and will?

Chiefly, you'll have to feel your own way with that. When you've accepted it, then you've cracked the entire thing!