The Irishman admitted a miss from the spot at Griffin Park in a 2-2 draw last season was playing on his mind as he stepped up to take another on Monday night - but this time he slotted it past Bees keeper Richard Lee.
"It was at the same end, probably about the same time to be honest," Mooney told Press Association Sport.
"It did play on my mind, I was nervous as anything. Even before the game, driving here, I was thinking 'which way will I put it'. I knew they would have been watching where I put my last one.
"To be honest I hit it that side last year and had it in my mind to put it the other way, but when it came to it I said I'm just whipping this as hard as I can and if he saves it, he saves it. But I hit it right in the corner so I can't complain.
"I think this year was a better penalty. Richard has saved a good few in his career but thankfully this one nestled in the bottom corner."
Substitute Shaun Batt grabbed the second goal to secure a 2-0 win, Orient's eighth successive victory, to leave them five points clear at the top, and Mooney insists they can keep their record-breaking run going.
"Of course we can," he added. "One or two games is a good run, three or four is a great run but eight is consistent.
"We've got a good side, players who have played at a higher level all across the board so there's no reason it can't continue. We just want to keep going for ourselves. We have a dressing room full of character.
"We've got another tough game on Saturday against Walsall, they are a good footballing side. They will want to be the first side to beat us and we have to live with that. But we've lived with that for eight games and long may it continue."
- Sports & Recreation