A professional trader who focuses their time on trading will certainly always trade when a good opportunity arises. However, a professional trader always knows when to stop trading and when to re-enter the market. Clearly, trading psychology is really more about self control or managing one’s ego and emotions, when facing the market. And even professional traders sometimes struggle to control these aspects effectively. However, they do maintain a strict schedule and time management routine to prevent themselves from trading excessively and to keep their mental state healthy.
I guess no trader can perfectly integrate good psychology into trading because human in nature will always have its negative traits and attitudes that can easily ruin their trades. The thing is, they can study how psychology works in trading, but they can never execute all-out performance into it, that's why there are traders that end up like gamblers in the long run.
And even professionals are never an exception. Yes, they have an edge when trading but we can't really tell that they have completely acquired trading psychology.