This simple question has many layers to it but in the answer, lies an opportunity for peace. The ancient Stoic philosophy explored and defined this idea of what we control extensively. What it comes down to is that all we have total control over is our voluntary judgments, opinions and actions. We have influence over other things and of course no control whatsoever over many things. So there are really three categories:
1) Complete control
2) Some influence
3) No control
It's very interesting to find yourself upset about something, for example, something in the past, ruminating about it, spending mental energy on it, and then realizing that you have no control over it anymore because it's in the past.
I find that I spend most of my time thinking about things I can't control: pandemic or business worries, how a family member is doing, news or politics, what someone else is thinking (can't get much more out of my control than that!) etc. Then I remind myself to "mind my business" and spend my time and energy wisely. It helped to make a list of all the things I can do that are in my control: paint, write an email newsletter to you, post my work on social media, yoga, go for a walk, take an online class, journal, meditate, work on my business, cook a healthy meal, ask a family member what they need, clean the house, take care of myself, the list goes on.
I understand well the urge to try and control things outside my control, the pull to get everything in order and make everything the way I want it. I also know that it's a recipe for misery, anxiety and tight muscles in my back. So, that's my practice these days, staying focused on my actions and judgements. By the way, the Little Book of Stoicism is probably my favorite introduction to this timeless wisdom so I created a link to it in case you're interested. 😊