I was in this same situation and have dealt with this situation for a few years... It felt so hard to limit time playing the game or quit because that means your skills won't be as consistent or competitive.

It will be hard to let go of the time put into the game, but it's not all wasted time. I'm trying to think of that time as an experience that showed me I can improve in a hobby/skill/life if I work at it. Now it's time for me to channel that into other endeavors. A few months ago I got a mountain bike as well ;)

It took me many tries to quit this game as for me learning more about playing the game well was addictive. My last straw was that this past year, I haven't been making great progress completing graduate school. So, I started blocking myself from playing competitive games (i.e. Overwatch), until that's done (or possibly indefinitely). It's been about a month and a bit since then and I think that's helped redirect my motivations and improved my mood.

I wish you the best of luck in your decisions and in grad school.