Retiring and not knowing who you are

The canon's inquiry into self is practical: if something were really yours, it says, you could make it be as you wish, and a role in other people's lives cannot be made to stay. That is meant to be seen, not recited, and it is often seen most clearly at a moment like this. The suttas also ask everyone to reflect often that they too will age. On practice itself they are unfussy: sit, hold the body upright, set mindfulness in place, and breathe. They do not tell you how to fill the days or whether to go back to work.

What the suttas say

Mendicants, form is not-self. For if form were self, it wouldn’t lead to affliction. And you could compel form: ‘May my form be like this! May it not be like that!’
The argument from affliction — if it were yours, you could make it stay.
Where this stops: Directed at monks already practising; it is not a reply to grief and should not be offered as one.
SN 22.59:2.1–2.3 · The Characteristic of Not-Self
Mendicants, a woman or a man, a layperson or a renunciate should often review these five subjects. What five? ‘I am liable to grow old, I am not exempt from old age.’ A woman or a man, a layperson or a renunciate should often review this. ‘I am liable to get sick, I am not exempt from sickness.’ … ‘I am liable to die, I am not exempt from death.’ … ‘I must be parted and separated from all I hold dear and beloved.’ … ‘I am the owner of my deeds and heir to my deeds. Deeds are my womb, my relative, and my refuge. I shall be the heir of whatever deeds I do, whether good or bad.’ A woman or a man, a layperson or a renunciate should often review this.
The reflection the Buddha asked everyone, monastic or lay, to make often.
Where this stops: Never preached at someone frightened or grieving; owning one's deeds is never a reason to call an illness or a loss someone's kamma.
AN 5.57:1.1–1.9 · Subjects for Regular Reviewing
‘The world has no shelter and no savior.’ This is the second summary. ‘The world has no owner—you must leave it all behind and pass on.’ This is the third summary. ‘The world is wanting, insatiable, the slave of craving.’
Raṭṭhapāla's four summaries — the reasons a young man of means went forth, given to a king who asked.
Where this stops: A renunciant's reasoning laid out for someone considering it; not a case that everyone should leave home, and the sutta is explicit that his parents were not persuaded.
MN 82:36.3–36.7 · With Raṭṭhapāla
It’s when a mendicant—gone to a wilderness, or to the root of a tree, or to an empty hut—sits down cross-legged, sets their body straight, and brings mindfulness to the present. Just mindful, they breathe in. Mindful, they breathe out. Breathing in heavily they know: ‘I’m breathing in heavily.’ Breathing out heavily they know: ‘I’m breathing out heavily.’
The first instruction in the Satipaṭṭhāna Sutta, in full and without elaboration.
MN 10:4.2–4.4 · Mindfulness Meditation
Mendicants, suppose this Ganges River was carrying along a big lump of foam. And a person with clear eyes would see it and contemplate it, examining it rationally. And it would appear to them as completely vacuous, hollow, and insubstantial. For what essence could there be in a lump of foam? In the same way, a mendicant sees and contemplates any kind of form at all—past, future, or present; internal or external; solid or subtle; inferior or superior; far or near—examining it rationally. And it appears to them completely vacuous, hollow, and insubstantial. For what essence could there be in form?
The lump of foam — looked at closely, it appears empty and without core, and so does form when examined the same way. The canon's way of asking for close looking without claiming that nothing is real.
Where this stops: Said to monks, and applied in turn to all five aggregates (feeling, perception, mental formations, and consciousness follow). It describes how form appears when examined, not whether a job, a marriage, or a life is worth anything, and it is not a reply to loss.
SN 22.95:2.1–2.2 · A Lump of Foam

Bring your own situation.