Acceptance that I cannot control everything, I can only control my own reactions to those things.
Focusing on what is directly in front of me, directly ahead of me, and trying not to overthink what might be around the proverbial corner.
Being as prepared as I can be should the worst happen - DH knows my wishes if I was ever in a position where I needed something like life support and knows my funeral preferences, I have life insurance, I have a will.
Reminding myself that the world have ever been thus and I am just a small part of a long process.
Taking time to appreciate and enjoy the little things. My loved ones know they are loved, I know I am loved.
Having been a position where I was physically dying of an acute illness that had gotten to the stage where it could go either way, mentally I reached a point of peace where I knew I'd done the best I could with my time, my DC would be looked after, DH would manage, and that it was going to be okay.
The human spirit and the human body are both remarkable things as is modern science. Obviously they all have their limitations but I've been through so much shit in my life and I'm still here, still smiling, still living a normal life. "It is what it is" and "keep plodding on" seem a really reductive way of summing it up but that's basically how I do it.
I have PTSD and anxiety so issues like uncertainty and dealing with bad things come up a lot in therapy.