Heisman Trophy winner Johnny Manziel of Texas A&M says he's learning every day about life as a celebrity.

The first freshman to win college football's top award said Thursday he was trying to avoid making "the same mistakes again" after a picture of him holding cash at a casino was posted to his Twitter account Saturday, a day after the Aggies beat Oklahoma in the AT&T Cotton Bowl. The picture was later removed.

Manziel responded to apparent criticism by tweeting, "Nothing illegal about being 18+ in a casino and winning money.KEEP HATING!" Speaking on a conference call to accept the Manning Award that goes to a top college quarterback after bowl season, Manziel said he wasn't growing weary of the scrutiny.

"I don't really pay attention to that stuff as much as some people do," said Manziel, who set SEC and Cotton Bowl records for total yards and helped the Aggies (11-2) to their best record since 1998. "I've got to learn from it and move on and make sure I don't make some of the same mistakes again as far as the stuff I've been doing."

Manziel was right about gambling being legal for anyone 18 or older at the WinStar casino, about an hour north of Dallas just across the state line in Oklahoma. It was a little murkier when the celebrity website TMZ posted a photo of the 20-year-old football sensation holding a champagne bottle at a Dallas club on Saturday night.