Yeah, it's supposed to do that. It's kind of a problem when you have to unplug the TV to get work done, or to change departments to avoid letting the hot coworker seduce you. It does have advantages when you're not very good at lofty decisions, though; you can see the problem with an organism that can just decide eating is wrong and starve to death.

People normally react to that by setting modest goals, acquiring the right habits to consistently achieve them, and then working their way up. Rewarding both systems ("After 50 minutes of work, eat a chocolate") also helps.