Your present self has to coordinate with your past and future selves. You might want to consciously, on-purpose simulate those selves in your mind in order to do this more effectively.
What does this mean? Here's a more concrete example: should you donate money now, or later? There's a complicated argument here about growth rates of whatever-you're-donating-to relative to inflation, but we're going to sail past that completely and assume you would be better off in some objective-ish sense donating later.
The problem then becomes one of trust in your future self: if you spend your whole life being a person who doesn't donate money to charity, how can you guarantee that the person you'll be after 50+ years of non-donation is the sort of person who will actually donate money at the most appropriate time?
This kind of problem seems to be fairly common, relating to weight loss, tidying your room, etc.