How do you force yourself to stay on a game until you beat it?

I have a struggle of completing games, always starting them, playing for a good session and getting a decent bit into them and then not returning even though I enjoyed the game. Opting for games that are easier picked up and played for any amount of time like roguelikes and lites, how do I convince myself to sit down on those longer story style games?

I said I wanted to beat more games this year, that didn’t happen so next year I really want to do that.