beat the third horse

Verb:

1. The act of going up against a rival that you did not see coming because they are otherwise known to be punks.

2. Any actions performed in excess that realistically should not be performed. For example, excessive masturbation to the point of turning one's skin raw, or done in an unkind manner.

Dave has been up in his room for a long time, he must have had a long week.

"$20 says he's going all out and just about to beat the third horse"