I used to pitch and be the TD (not judge) in my tournaments, but now with my arthritis I am no longer pitching. I miss pitching, but now I am far more relaxed just being the TD (and now judge) at my tournaments.
If I am pitching and (as a judge) making a ruling about any other pitcher who's in the same class I am, it could indirectly affect me. Allowing or denying a point or ringer affects their score and then possibly benefits me if I denied them points.

My motto: 'Not only do you have to be fair, you have to appear fair.'
That is, if you are as fair as you can be in your decision-making, only you know that. You also need to appear to be fair so everyone is comfortable with your rulings.