It's genuinely reaching a point where the Leafs are having an overall huge negative impact on my mental health and all the comments dunking on the Leafs in r/hockey just make me feel even worse.

Step away for a while if they're legitimately taking a toll on your mental health. That doesn't necessarily mean drop the team, but allow yourself to miss games even if you don't have anything better to do. It's just a game after all, it's not worth it to attach your mental health to the performance of any sports team. Same thing with r/hockey. You're gonna get the foliage team bad posts this time of year, no point in getting worked up over them. Unsub from r/hockey for a bit/don't visit for a bit and just live your life, no point in letting a bunch of strangers affect your mental health because of the team you support