I see people time and again spending their energy on being angry, or trying to please unappreciative other people, or insisting on being right when actually it doesn't matter at all, other than to their egos, or hanging onto their resentments for dear life, because it's the only way they feel better about the wrong they think they have suffered at the hands of the object of their resentment. These all drain energy, and plenty of it.
But guess what? If the energy has been used up being something less than our most noble selves, there isn't enough left to be truly our highest and best selves. If you are using up energy fighting, resenting or sulking, where will you find the energy to love yourself or indeed anyone else with all your heart, or the energy to be truly creative, or to bring your best part to a relationship, or to put all of yourself behind your career, a project or anything else that matters to you?
I can think of a couple of times in my own life when I have goofed badly and then spent hours, days, weeks, months expending energy on beating myself up. Whilst I was doing that I didn't then have sufficient energy reserves to bring all of myself to my relationship, to look after my health properly or to keep responding proactively to everything else that Life was presenting to me. The result: a downward spiral of under-performance in most areas, except of course in the self-pity area.
The question then is: where do you expend your energy? Is it in the furtherance of creating something more or bigger with your life, or is it in furtherance of looking after your ego and dealing with things which ultimately don't matter?
Explore what truly matters in your life and put your energy there. You'll be so glad you did.