eat or be eaten
You either be the wolf or the sheep. Life's a big field and if you don't run fast enough, the wolves will just eat you for breakfast.
I worked my butt off all week. My coworker took the credit and now I'm stuck doing the boring stuff.
I stayed late to finish my work. My boss left early and I got stuck with all the extra tasks.
I didn't show up to the meeting. Now I'm stuck with the worst tasks and no one even knows I exist.