Still playing a non-soulslike, Isles of Sea and Sky. Once that's finished I might get into Code Vein.

My first one was DS3 and there were two lessons that helped me;

One, to let go of souls and stop caring about them. There are always more. It's not worth the time or stress to pick them up every time, and once you lose them the burden is lifted.

Two, for tough bosses learn their moveset. Don't attack, just practice dodging and watching them until you understand them better. Then after a few rounds of that, start to attack when you know your openings.