when do video games you like start to become boring?

A really awesome game you've been playing everyday and suddenly after a year you become bored of the game and stop playing it, What causes you to lose interest in the game you were playing?

I think it might be different for each person. But for me, I was in the middle of playing a PS2 game Radiata Stories & I couldn't for the life of me figure out which side I wanted to be on. So I didn't play it for over a year (or more) before finally deciding which side I wanted to be on & went back to the game & was finally able to beat it sometime last year.

With Xenoblade Chronicles X; I think once I finished making my character & getting into the main area where I was lead to go to, & getting into the group who seemed to be rallying after my attention I got bored with it because from what I've heard it's going to be about 12 hours (or more) before I get a giant mech & I'm a bit impatient. I think if there was more of a story involved I'd probably go back to it, but atmo I'm just 'meh' with it.

The games i play become boring after either getting stuck at a really hard puzzle of the game.