By Jack Douglas Jr. | CBSDFW.COM

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DALLAS (CBSDFW.COM) – A contrite Johnny Manziel, dressed in a suit, shirttail out, entered misdemeanor court on Thursday where a judge reminded him: “You’re an adult. You’re a grown man.”

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It was a fitting reminder for the Heisman Trophy winner whose star once shined so bright.

Manziel was in court in Dallas on Thursday on a misdemeanor assault charge involving an ex-girlfriend — the latest chapter in a series of escapades that have cost him a great job in professional football.

(credit: CBSDFW.COM)

(credit: CBSDFW.COM)

Judge Roberto Canas told Manziel his job was to make sure “everybody stays safe,” including the former Aggies quarterback and his ex, Colleen Crowley.

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Manziel can’t go near her, he was told. He can’t text her, email her, write her a letter. “You can’t try to follow her, or anything like that,” Canas ordered.

Flanked by his lawyers, head bowed, the often flamboyant Manziel replied: “Yes, sir.” He also promised the judge he would not bring a gun into North Texas, and said he had no weapons at his home — wherever that is now.

The hearing lasted less than 10 minutes, and then the judge told Manziel to have a nice day.

The fallen football star, just 23, then walked into a hallway of TV cameras, his only blockers being the two lawyers who led him from court.

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Follow Jack Douglas Jr. On Twitter: @JackDouglasCBS