UFC fighter Justin Jaynes bet his entire $25K fight purse on himself and LOST ... so, instant regret, right??
Nope ... 31-year-old JJ tells TMZ Sports he'd do it all over again -- and that's exactly what he wants to do.
"I really don’t have any regrets man. I live high risk, high reward kind of lifestyle."
Of course, Justin famously gambled his fight check ... and ended up losing a 3-round split decision to 34-year-old Charles Rosa at UFC Vegas 30.
And now he wants that cash back -- and he's willing to fight Rosa again.