In the dying seconds, Leinster were camped on the Saints line but when attempting to work the ball wide, Heaslip knocked on and Jamie Elliott ran the length of the field to score, denying the Irish side a bonus point.
"I knocked it on, I didn't execute, I knocked it on," Heaslip, who is to be rested for this weekend's clash wth Edinburgh, told the Irish Independent.
"He (Elliott) ran the length of the field and scored a try. How would you feel? It wasn't exactly a punch-your-fist-in-the-air kind of moment.
"Sport is a funny one. In a typical rugby season you probably have, what, 15-20 big games and some you win, some you lose. You want to win them all, that's the mindset you go out with.
"Sometimes it happens for you, others it doesn't go according to plan and you have to grind it out. Sometimes you do and you get the win and sometimes you don't.
"We have a lot to learn from that game going forward and the lads have a chance to be able to do something about it this week in Edinburgh.
"Yeah, it wasn't pretty and the review wasn't exactly great to be in, but you dust yourself off. There are so many games that you just have to get back up on the horse again.
"You have to look at it analytically, at the positives and the negatives. We weren't as accurate as we could have been at times and that's what happened at that level. They are a bloody good team and they showed it."
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