Completion

I know that many people feel compelled to: achieve 1000/1000 gamerscore, obtain a Platinum Trophy, or otherwise finish a game with 100% completion.

This can produce a wonderful sense of accomplishment, and, in the case of some games, your utter mastery of the game. However, sometimes that's not what happens.

Some games will create challenges so mind-bogglingly stupid, it's a wonder a human being created them at all. In these cases, going for 100% completion can lead to an extreme case of wasted time and, at the end of the day, still leave you without mastering the game; you may not even be enjoying your playtime anymore.

As a good rule of thumb: if it's necessary to look up directions outside of the game, it's probably not going to be worth it.