What you're going to notice a lot for people that are less consistent is that your muscles aren't performing at the same strength so you're overshooting a LOT or very unfocused.

You can really notice this right away if ur playing far from your game, while playing aim maps, mix or scrim. Your timing and movements from your arm are not in good sequence.

To help this you should take the time to let your muscles become in unison with your brain. So if you are or are not an active person, on your OFF days where u are playing poorly u should really step back from the GAME for about an hour.

Do shoulder, bicep,tricep and chest workouts(pushups). Try to use weights that will make you work hard and become focused.
Create a small Regiment of about 30-45minutes of working out.

When you are working out remember to pace yourself and don't overdo it, ex: THROWING YOUR ARMS AROUND WITH WEIGHTS.

Go SLOW and in CONTROL for all your workouts. Quality over quantity. Once you start losing your form and you can't push yourself any further then you shouldn't force another rep using poor form.

This will help you get in control of your body and help you focus.

After you're done all of your workout, take time to focus on the game. Watch a NEW demo of a player you like; on a map you're going to be competeing in or you want to learn something in.

Now that you are fully focused you will perform at a higher level than before don't forget to jump back in the aim map for about 20mins max u don't want to kill yourself before your matches or practices!

Goodluck have fun!