Hello
When I was newer, I also felt like my AoP was struggling to stay permanent. Until I did one for a full year straight.
Set your mind on one, and word the affirmation the best way (you can ask here for advice), and stick with it for a full year. You can add other AoP through the day on top of it, I do a main one and a shorter one either at night or first thing in the morning.
After the year is complete, you will likely feel like you can change it without it going away.
And anytime you feel your AoP is a bit weak, take a moment to tune in to your aura and tell yourself firmly that your AoP is very strong and effective.