You don't want to become a secret service agent

Well, maybe you do, but this article from the Washington Post on their training techniques may dissuade you:

Within seconds of entering the mat-room bar, Krista's partner, an Army National Guardsman who earned a Bronze Star, is knocked to the ground. A role-player drags Krista across the floor by the cuff of her pants. He straddles Krista and punches her.

"Get off me!" Krista screams.

"Get ready to die!" the music screams.

"Keep fighting!" Mixon screams.

The role-player twists Krista's arms around her neck and pulls, choking her with her own hands. She gags. Her nose is bleeding. Her cheek is bleeding. Blood blisters on her legs, bruised by training bullets while chasing assassins through the woods, trickle and ooze.

On her back, in the dark, Krista watches the role-player's face swirl into darker shades of gray. She is losing consciousness. Mixon yells, "Do something!"

It's long, but it's an excellent read.