My advice to you is that everyone makes mistakes or does things (or maybe allows things to happen, like this instance) that they regret or that don't make them feel too good. Just "start from scratch" so to speak: turn a new leaf, turn the page, and move forward knowing that you have learned from this and that you are now stronger and wiser for having gone through it. Don't allow the memory or the bad experience to "beat you up" - look forward and not back. However, do use the experience as a reference point for the future. When you see things like this starting to happen again in a different situation, you'll be able to recall your experience and you'll react much better, stronger, and wiser next time. I have a great mentor who says, "When something bad has happened and you're feeling really down on yourself, just remember that ZERO isn't a bad place to be. When you're at ZERO, it just means that you've been knocked back down to "ground level". It means your feet are planted firmly on the ground, you're probably in a place of humility (which is good), and you're in a place where you can start building something good again - from the ground up."
Sounds like this was one of those experiences for you. Your colleague knocked you down (and as you say, you "allowed it"), but that's OK. Now you're at ground zero, you pick yourself up, and you don't condemn yourself. You just start building from where you're currently at and know that you can build something great when starting from the ground. When building a house or a building, that's where the foundation must be layed - on the ground. Zero is a good starting place. It gets you back to the basics of life. Remembering how to enjoy life and what's really important again.