To stay on top of = To get under control
When I get busy it's very difficult to stay on top of all my paper work.
To get to the bottom of = To find the original source of the trouble
My P.C. is not working properly and we can't seem to get to the bottom of the trouble.
Binge = In excess or too much
Binge drinking can often cause lack of memory.
A snooze = A short nap
There is nothing that feels better than a short snooze in the afternoon.
True grit = Staying power, fortitude
One must have true grit to get through these tough economic times.
To mull = To think about for a while
I am still mulling my summer vacation plans.
To buckle down = To try hard in a concentrated effort
To be successful at anything one must buckle down and give continuous effort.
To hang it up = To retire
After 20 years in the major leagues he decided to hang it up .
To tie down = To contain, delay, or hold back
Paper work often ties me down on the weekend, so I seldom have time to hang out.
A buff = Devotee or fan
As I am a weight lifting buff, I constantly read about new training ideas.