`C` was the last commit you pulled from `origin` and D, E and F are commits you just made but should have been in their own branch. This is what you wanted:
Okay, you're `master` is now back at `C`, which you lasted pulled, and the `my_feature_branch` includes D, E and F. Just checkout `my_feature_branch` and continue work as usual. I'm sure no one saw what you just did.