Why do options sometimes help but other times hinder?

Why are some things harder when you have to do them but other things are harder when you don’t have to do them?

  1. Like if I have to go to a party, it seems much harder. Or if I have to write a paper, it’s always harder than if I’d done it on my own.
  2. On the other hand, it’s harder to sprint full speed when I don’t have to. It’s also harder to get somewhere on time when I don’t really need to be there.

Something about freedom makes those first situations easier. Something about motivation makes those second situations easier.

Why is that? Why are some things the first type and others things the second?