Getting better at "laddering"

Catherine suggested using “laddering” when trying to substitute negative thought for a positive one. The approach completely made sense, but I’m still struggling with the first step. Here is the example I’ve used: Negative thought “My boss is completely unqualified to do his job”, desired thought “He is doing the best he can”. Catherine suggested adding “… and its okay” in the end of the negative thought. It really helped to “defuse” the initial during our session, however when a new circumstance came up a few hours later and my brain immediately went back to “My boss is completely unqualified to do his job” and totally resisted “My boss is completely unqualified to do his job and it’s okay” and responded with “how this possibly can be okay?”, “Is his boss completely unaware of this” etc etc etc.
I’m not sure if I need to come up with a better intermediate thought to make this neutral or is there another tool I could use since this seams to be a pretty deep pattern.

Thank you so much!