"Accept being unimportant.
Do not be concerned with loss or gain."
"WHAT?!?" you say. "WHAT DO YOU MEAN I'M NOT IMPORTANT!!!"
Well, you're not. No one is important all the time and everywhere. Everyone is important sometimes and in some places. But we don't have much trouble accepting that. The trouble is accepting the experiences in between, when we're not particularly important.
In the big picture, we can't be that important. Our lives are relatively short, and we are very small, and this universe is very old and very big. What we get stressed about, then, is our relative importance compared to other people. In this game we play, every little loss and every little gain translates into a tiny, perhaps imaginary, change in our relative level of power and importance in comparison to others. This is a great way to torture oneself.
Quitting this game is liberating. Even if you've spent every waking moment trying to convince yourself and others that you are important, even if you can't imagine existence without it, even if you think life will be meaningless without this struggle, you will feel liberated. Existence will continue. Life will be more or less the same, minus the stress and wasted time. In their place will be rich new experiences, opportunities to connect with people and create the kinds of relationships you once thought could be earned only through becoming important.