Hey Johnny,
First of all, make sure to practice just the strum pattern by itself, without any chords. Mute your strings and just focus on the pattern.
Secondly, you can count the beats out loud with your voice. It may sound silly, but it will help you focus. And say “1” and “3” louder as you do it.
Also, you can rock your body as you strum. I’ll discuss your question on this week’s live class so you can see what I mean, but putting your body movement into your practice is another way to help you focus, as silly as it may look.
You can also try to follow along while I play Rock Of Ages, but just with the strum pattern.
Hope these tips help you out!
You never fail until you quit!