"Toughen up Tinkerbelle"
"Grow a pair, son"
"Who wears the pants in your relationship?"
"Just do it" (proudly swiped from Nike)
Or, for me, "Put on your big girl panties."
It's the equivalent of 'shut up and get it done.' I partially agree. It's great to think things through, but things have a habit of happening when you are in the act of doing rather than thinking of what to do.