Set yourself a goal that you can fully accomplish today, then go do it.
Maybe you need to mail a letter. Not eat after 7:00 tonight. Make it through the day without raising your voice and cursing.
I suspect everyone has these immediate things that would feel great to accomplish in short order. They aren’t overly difficult, it just takes a little concentrated effort.
I also suspect that successfully navigating those small goals will set you up to do greater and greater things.