Time To Get Shit Done. Right after ejaculation after an intense session of masturbation, man is quickly thrown back into reality, upon which he is reminded of all the errands he must run, all the work he must do. When motivation is scarce for said things, saying a cool, short, hip abbreviation, such as "TTGSD" will provide the energy needed.
Often also altered to "Double T, GSD".
Chad: Dude, i just came so hard jerking it to Tina's bikini pic. I swear, her photos are better than porn.
Dale: Ditto, dude. Absolutely right. Well, anyway, TTGSD, I guess.
Chad: Yup. TTGSD. See you at the gym.