Hey and how are ya, from one gamer to another. I absolutely understand your predicament; once the game starts, you become completely immersed in a different world that requires 100% of your concentration...a few hours seem to evaporate in the span of a few minutes. I have a hard time quitting (a former shrink attributed this quirk of mine to OCD), and especially when I'm in dire need of escapism. What I've learned to do is make a list of tasks that need to be completed first, ordered from highest priority to lowest. Pick your top three and start on them immediately. You can reward yourself with a "game break" when you've finished. If you have a longish list, give yourself a 30 min. - 1 hr. game break after every three tasks completed (unless you have one task that's a sizeable time investment; the idea is to break up the monotony of task completion with rewards).

If getting on the computer is a trigger, try to stay off it until you're ready for a game break.

If I'm obsessing about a game and find it too difficult to focus on task completion, I'll take a break from gaming for a week just to clear my head and reset my brain. I always feel like I get my self-discipline back after these mini hiatuses.

Good luck!