The reason that judging drives you mental is because it tangles you up in good and bad. It could be that being tangled in good and bad makes you judgmental, but either way, your are tangled, judging and going mental.
Being caught up in good and bad is not bad unless you are caught up in it. If you think that there is something wrong with you because you are caught up in good and bad, then you are judging yourself, which is how judging drives you mental.
Once you recognize that you are mental, judging and caught up in good and bad, you begin to untangle yourself. As you notice yourself judging others or yourself, you can notice the judging event. You are the judge, jury, condemned and/or acquitted. Who and what you judge is not so much a reflection of them as a reflection of yourself. The reflection is neither good nor bad except as you judge it to be.
If each time you judge, you step out of your subjective robe and see that you are also the object of judgement, you find compassion in the mix. You see the good along with the bad and stop worrying if you might be mental. Sentimental, instrumental, ornamental, fundamental, or just plain mental, who’s to judge?