Chris Sacca, an early investor in Uber and Twitter and founder of Lowercase Capital, announced Wednesday he's "hanging up my spurs" and retiring from venture capital and "Shark Tank."

Sacca said he recently rediscovered a notebook with entries he had written back in his 20s. In it, the younger Sacca had said he planned to retire at age 40. "In a matter of days, I'm going to be 42 years old," Sacca said. "Two years late."

"I succeeded at venture capital because, for years, I rarely thought about or spent time on anything else. Anything less than that unmitigated full commitment leaves me feeling frustrated and ineffective," Sacca said. "As you've heard me say on the show, if I'm not all in, I'm out."

Sacca said Lowercase Capital will continue to support its current portfolio of companies. "We just aren't going to invest in any more companies going forward and we won't be accepting any money from investors," Sacca said. Matt Mazzeo, Sacca's partner, has said he has something "exciting to announce soon," though details on that weren't revealed.

Sacca said he's leaving ABC's "Shark Tank" this season, since he can't do the show while also keeping to his promise to stop investing in new companies. Sacca said Mark Cuban was most bummed about his decision to leave.

Correction: This story was revised to clarify that original episodes of "Shark Tank" are aired on ABC. CNBC owns the exclusive off-network cable rights to the show.