The former Celtic midfielder has appeared in the Champions League and Europa League, but Sunday's Scottish Communities League Cup clash with Hearts is a first for the 25-year-old.
McGowan is aware it could also be his last – and he wants to make sure he has no regrets.
"Speaking to some of the boys, it's their first cup final," Gowser said. "It's my first also. Some players don't even get to play in a final.
"You just need to make the most of it. Some of the players who played in the last cup final are still here.
"That was a hard time for them when they got beaten by Rangers, who were down two men. That still hurts some of the players and they want to make amends."
McGowan and St Mirren showed they could handle the big occasion when they beat Celtic 3-2 in the semi-final. He added: "We just know it's one game, it's cup football and anything can happen. Hearts will be saying the same thing as well.
"But we will do our utmost to stop them and hopefully we can bring the cup home to Paisley."