I have got a lot better at this than I used to be. I used to buy all sorts of games on launch, even when I had a few others on the go, and then they would stay unplayed sometimes for years. An example, I still haven't got round to playing Nier Automata and I bought that when it launched.
I think it used to do it because I still thought I had loads of free time like I had when I was at school/university, and over the years it has finally dawned on me that with work etc, my free time is minimal. I sometimes slip back into the impulsive purchase, the Division 2 springs to mind. I bought it, and have only played it a couple of times but overall I pass on way more games than I used too.