To take control of your situation.
Imagine you are
stuck and would
push ahead with your hands. Now imagine you are grabbing your ass with both hands to
push yourself along.
Or grabbing your ass with both hands to lift yourself out of a problem.
Similar to pulling yourself up by your bootstraps, except more evocative.
My crisis-prone
neighbor was
whining about her latest self-inflicted fiasco.
I told her "grab your ass with both
hands" and went out for a beer with my friends.