Why not?

Consider it aspirational thinking.  I signed up today for a 5K on Saturday morning.  I'm probably not ready for it, but why not run it?

My arms are still sore from training sessions this week.  I'm going to be busy working for a good portion of Saturday.  Taking that time in the morning to get some extra sleep or just sit at home and be wouldn't be such a bad idea.

Instead, I'm going to wrench myself out of bed before 8 a.m. and attempt to run this entire race.  Wish me luck.