Hi, Dan. Welcome.
You ask a very good question. If there were any easy tricks, I'd give them to you. One thing you can do is to make a big effort to be aware of when you are negative or critical. If you can catch that thought and put a mental STOP sign up, then you can substitute another behavior. For instance, we all know that encouragement and praise go a lot further with a child than criticism and fault-finding. If you can find something good to say instead, you may "nourish" a positive outcome rather than feed a downward trend.
I don't know if this applies since you didn't give any example, but another trick is to worry about the things that are yours, and leave to the others what is theirs. Hope this helps.
