trust in yourself
This is the crux of everything. We have been taught that we are inherently bad, that something is surely wrong with us. We look for our faults, and of course find some. In fact, if we were taught to simply operate according to what we genuinely feel, taught that we are intrinsically good and wise, we would be much more loving and positive beings.
I don't think there is anything terribly wrong with justifying actions though. A little extra thought wouldn't hurt, as long as we stay true to ourselves, and are not justifying to make our actions palatable to someone else. Things get terribly complicated then as you say, manifolds deep. You do you, let others do themselves. There's far too much emphasis on trying to find the one, absolute, proper way to be now. In fact, there is no one proper way to be, think, or act.
I agree on this that people think of themselves being bad - I would ad "without knowing it". That is actually something someone would not believe. I only realized it myself after studying books and doctrines and started to listen to my self talks (inwardly). Something happens and you curse yourself, give yourself bad names and such. That is actually important to notice that when the inner judge speaks, that it has a meaning and an effect. If I myself judge me in the harshest ways, it's no wonder I do it with others, too.
It takes some self realisation to become aware of this habit.
Giving justification is totally okay. When someone asks me I can admit that I maybe am not really certain, why I decided this or that way. That there might be reasons and that I suspect it maybe "this" or "that". That usually opens a conversation and my counterpart has the chance to have a good talk with me. Instead of having to jump at my missionary statements. :) LOL
I mean, have you noticed? When you make statements (without having been asked) it usually goes into a not so nice direction.
My inner voice was cursing others when I thought badly of myself. I have a more loving inner dialogue now that I've realized that I am normal, and so are most others. The current sentiment, driven mostly by the left, that we must all think alike, that there is one truth, is false.
I hear you. Modern people are neurotically obsessed with anxiety of becoming old or die of some sort of disease. While this is exactly what happens and will happen anyways, no matter what one wants to avoid or "prevent". I know of no one who died "just so". LOL :D