I have personal experience with this and wrote about it here - https://news.ycombinator.com/item?id=39394432 Others might also find it useful. I think of it as my "second career" and am now looking at what to do for the rest of my life as a "third career".

As Humans with strong bonds to others it must be thought of as "Our Duty to Do" and in particular; Filial Duty is paramount (assuming "normal" Parents).

Lessons learned and Advice;

1) It will be very difficult and exhausting both Mentally and Physically (we are designed to be selfish and altruism is hard). But you will have to develop "mental attitudes and physical behaviours" to cope with all circumstances and build up fortitude.

2) Techniques from Philosophy and Science should be employed to develop proper attitudes and behaviours. For example from Tibetan Buddhist "Mind Training" practices (Lojong - https://en.wikipedia.org/wiki/Lojong and Tonglen - https://en.wikipedia.org/wiki/Tonglen) one can train in compassion and willingness to suffer for others so that we can always maintain a positive outlook (this is key). See the book Essential Mind Training: Tibetan Wisdom for Daily Life by Thupten Jinpa for some of the original Tibetan texts. You should also read the works of Stoics Epictetus, Marcus Aurelius, Seneca and Cicero for developing mental strength.

3) On the physical side, set up your daily schedule around the patient's and do things together as much as possible eg. eating breakfast/etc. together, watching movies/just talking/going out/etc. together so that they never get a sense of being "alone and abandoned". Make sure to have a proper nutritious diet and take frequent naps/entertainment during downtime. You are not giving up "your wants" but merely re-scheduling it around "somebody else's needs". Do/Maintain proper Exercise (light and not too heavy) so that you are in good health and do not have to worry about yourself (this is key).

4) Time is finite and in order to do the above you will have to give up somethings you love and like to do. Be strict with yourself and give up all "your wants" which will hinder your duty and only add them in if you can make time for it without hurting the "patient's needs". Be clear in communicating your duties to others(friends etc.) so that they understand your situation and can maybe help as needed. You have to establish a new equilibrium with your environment.

5) Periodically you will fail in your caregiving and blame them/others (we are selfish animals after all) but that is ok as long as it does not become frequent and a pattern/habit. Catch yourself slipping on "your duty" and get back on track and show you mean it with extra care talk/action.

Finally; always remember that nothing can overwhelm you unless and until you allow it to. Everything can be managed with knowledge, action and discipline.

Caring for yourself while caring for others