A tip to fight FOMO - Make a priority list!
So back during Rafayel's birthday I was really struggling with FOMO with his first years birthday card. It took me 110 pulls to get this years memory, and I put another 110 to his old birthday memory and I was at 8k diamonds crying how I was going to miss out on his first year birthday card. Yes, he took me 3 times to hard pity and lost both 50/50s.
Then I decided to make a priority list for myself since I only pull for Rafayel and realised I really should keep my pity for whatever is coming next for a rerun.
I have watched all of these on Youtube, but of course I want to own them all. But this list put everything to perspective for me - I can't miss Sea God. I realised that card was probably the lowest priority for me out of all his memories, so I stopped at 26 pity with guarantee for the rerun banner.
A lot of FOMO can be fought off with some planning - determine what cards are the most important to you and why. and how willing are you to miss out on those cards. For me, the old cards actually hold more combat/collection value rather than I would want them for the story. Of course this could be different for you, and that's okay! As long as you can make your own list and priorities, it's easier to shift your focus on the cards you find important. The FOMO will suck as always, but hopefully this would make it easier to skip certain banners you don't need at all.
If you're curious about my list, here's my reasoning: