I care about my family.
Even if there are some bad bits, I find that I still care deeply.
Mortality definitely motivates me sometimes. Rather than guilt, it is gratitude that I feel towards the love and care I've experienced.
You can also appreciate people without absolving them of their misdeeds or character flaws. They are not mutually exclusive items.
Even so, I can't fully explain why I care so deeply.
At the least, I know that I choose to not be bitter, to appreciate what I have, and to see people as people. Perhaps these factors express my desire for good relationships - which sounds fairly meaningful.