Generally I do my best to carry no regrets. Seems like a monumental waste of emotional energy to me when doing so.
Honestly though there are times when I do experience regret; but I view those moments as a time to take a moment to assess things and learn from them. If I'm too angry to think straight; I may defer reflection upon it until I have cooled and more facts have been unearthed. I may have been wrong in that moment.
A rookie mistake or a learning curve isn't going to phase me. I know I'm going to screw up; I hope others do as well. More often than not if I'm being silent; it means I'm silently learning, but I always need time to think it over first before I change my view.
Do I carry any regrets? Yes; I ultimately do end up carrying some. But those are powerful learning moments I remember. They aren't petty things. When I rationally look at all of my regrets they wash away, in the heat of the moment, as fleeting memories of youth often do. I may have been "right" as I could have been expected to be in my inexperience, which is to say that I definitely was not infallible in that moment and that I still had yet more things to learn.