I found the Will Young song "Stronger" quite motivating on days when things are all going pear-shaped
"It only makes me stronger when you say I won't succeed.
I'll work that bit harder when you say you see no strength in me.
The barriers, I'll break 'em down,
I'll prove myself, I'll stick around,
I'll get through it all somehow.
Nothing's unreachable.
Oh, it's just a state of mind.
If you set yourself up to fall,
You'll never get there at all.
All you've got to do is rise,
It takes more to break me than a wave or two,
Whatever set to test me gonna make me through."