You spend time on reddit because you want to. It seems unproductive to tell yourself that you don't.
You have a cognitive disonance, logical contradiction that you just need to bring to the surface and follow through. When you are about to reddit ask yourself whether you want to or not. Not some idealized version of yourself in your head. Just what do you want right now.
Then debug, introspect. Eliminate wishful thinking and accept reality - more time on reddit less time for other things. Do I want that?
Answer yes is perfectly fine. You do what you want anyway, but in my case simply bringing these contradictions to my conscious mind (and sometimes looking for a moment where it is exactly - like, I know that it's A or B I can't be spending time on both things at the same time, If I want to learn X it requires time) is enough to eliminate them.
I still spend time on reddit (not that much), but I don't think I'm doing anything I don't want to do or that it would be better to do anything else.
We are always doing what we want to. Telling ourselves that we don't is needless suffering.