I let inspiration arrive organically.
If I'm bored with a project, I put it aside and do something that interests me. In a day, or a week, or a month, or a year, I'll come back to it with fresh motivation.
The exception is if there's a looming deadline. Typically this is because a baby is on the way (or was born a month early... I'm looking at you, Lilly.*) or because someone is getting married and I bit off more than I could chew with regards to finishing their gift (or they eloped two months before the wedding was supposed to be planned... Michael, you inconsiderate jerk.*). In those cases, I generally spend some time kind of meditating on how important the recipient is to me before I get to work.
Seeking inspiration elsewhere is how I get even more UFOs in my craft room.
*said with mock-grumpiness and greatest affection for the individuals involved.