I originally encountered this idea on a Tim Ferris podcast, where he shared a chapter from the book 4000 Weeks: Time Management for Mortals. The tl;dr is essentially in the grand scheme of things (the past, present and future of our universe) we do not matter. This is not to be taken as an endorsement of nihilism and a recognition of the fact that nothing matters but rather as a tool for letting go and enjoying your life:

"Because once you remember the stakes aren't anywhere near that high, you're free to take meaningful risks, to let unimportant things slide, and to let other people deal with how they might feel about your failing to live up to their expectations."

This has been one of the most valuable concepts I have been introduced to this year and one that I meditate on daily. Whenever I am over-thinking things or replaying situations in my head I think about how in reality it does not matter, that is to say, the social cue I missed or the mistake I made at work is not important in the grand scheme of the universe and my action or inaction in that situation will most likely not be remembered. Once you are able to let go, you find it easier to be present in each moment and enjoy your life because in reality most of what you worry about isn't really worth the worry.

So, sit back, relax and let go cause you don't matter (and that's actually kind of awesome!)