I have this issue with motivation. I need to clean my house, but I have a difficult time getting myself to do it, unless I think I can finish it all at once. For example, based on past experience, it takes me around three hours of focused effort to get things from where they are now to satisfactory, but I only have ninety minutes. While I could get half-way there now, and finish up sometime later in the week, I imagine myself working hard for 90 minutes, and still having a messy house. Then I do something else instead, unless I'm in a state where cleaning seems less unpleasant than usual.

Does anybody have advice for combating this problem?

(edited for a typo)