Retaining courage during mediation

sounds like what Buddha described as Piti (litteraltraslation is "excitement"). It comes with first jhanna. it will be gone when enter 3rd Jhanna.

"There is the case where a monk — quite withdrawn from sensuality, withdrawn from unskillful qualities — enters and remains in the first jhana: rapture and pleasure born from withdrawal, accompanied by directed thought and evaluation. He permeates and pervades, suffuses and fills this very body with the rapture and pleasure born from withdrawal. There is nothing of his entire body unpervaded by rapture and pleasure born from withdrawal.

"Just as if a skilled bathman or bathman's apprentice would pour bath powder into a brass basin and knead it together, sprinkling it again and again with water, so that his ball of bath powder — saturated, moisture-laden, permeated within and without — would nevertheless not drip; even so, the monk permeates, suffuses and fills this very body with the rapture and pleasure born of withdrawal. There is nothing of his entire body unpervaded by rapture and pleasure born from withdrawal...

Be very aware of the changing nature of the sensations. And stay equanimous. Awareness (Pali: sati) and equanimity (Pali: upekkha) are the two wings of vipassana. Awareness of the changing sensations and equanimity of the experience of the law of anicca create wisdom (Pali: panna).

Bhikkhu, not necessarily to be a monk, who is afraid of Samsara(round of birth and rebirth), must do insight meditation with relentless effort that even all your energy run out, (be courageous like a lion). If one feels scared, just meditate scare/fear , just keep faith in Dhamma, it will go away because nothing is permanent. If still there is, remember the Arahan(one of the nine Qualities of Buddha) , and take refugee in Buddha again and again. Sometimes one is in the sixth stage of nana (knowledge of fear), then keep on meditating leads to higher stage of nana and overcome it.

" For every action , there is an equal and opposite reaction ". This is a Fundamental law of Physics and is applicable to Human Mental activities.
If fear comes as a reaction to the feeling of Intense Love ,you have to Absorb these reactions . Assume that these fears are Unreal and Temporary,wait for some time and allow the fears to die down .And then , continue with your daily activities--in this case--Meditation.

Because the "I" still interferes with those meditative states. Do not hold on to self-identity and your meditation would go much smoother:

Bhikkhus, how do you conceive it: is form permanent or impermanent?" — "Impermanent, venerable Sir." — "Now is what is impermanent painful or pleasant?" — "Painful, venerable Sir." — "Now is what is impermanent, what is painful since subject to change, fit to be regarded thus: 'This is mine, this is I, this is my self'"? — "No, venerable sir."

"Is feeling permanent or impermanent?...

"Is perception permanent or impermanent?...

"Are determinations permanent or impermanent?...

"Is consciousness permanent or impermanent?" — "Impermanent, venerable sir." — "Now is what is impermanent pleasant or painful?" — "Painful, venerable sir." — "Now is what is impermanent, what is painful since subject to change, fit to be regarded thus: 'This is mine, this is I, this is my self'"? — "No, venerable sir."

"So, bhikkhus any kind of form whatever, whether past, future or presently arisen, whether gross or subtle, whether in oneself or external, whether inferior or superior, whether far or near, must with right understanding how it is, be regarded thus: 'This is not mine, this is not I, this is not myself.'

"Any kind of feeling whatever...

"Any kind of perception whatever...

"Any kind of determination whatever...

"Any kind of consciousness whatever, whether past, future or presently arisen, whether gross or subtle, whether in oneself or external, whether inferior or superior, whether far or near must, with right understanding how it is, be regarded thus: 'This is not mine, this is not I, this is not my self.' ~~ SN 22.59 ~~