I've thought a lot about this "consistency thing", things that help me stay consistent are:
I try to not play TOO much, but also not too little.
I also believe "off days" are 100% mental errors, so finding out what makes you have off days and possibly correcting that will relieve you of the problem.
A big thing is focus. Don't underestimate it. This may sound silly/go without saying but always try your best when playing and be 100% aware of everything around you. For me at least how I warm up will result in how well I preform in matches/scrims that day.
Another thing to add would be keeping your cool while playing, if I'm frustrated with my performance knowing I can play better than I am, always saying to myself "wow I should have hit that shot". Obviously doing this won't help. Try to just play, don't over think anything. From my exp it'll just result in frustration.
My 2 cents.