Agree with this.
I measured my mood twice a day for 2 months using a similar app on Android. I tracked 10 variables on a +/-10 point scale I think (excitement, contentment, anxiety, etc.)
Turns out my mood just oscillates around a baseline of about 7/10 pretty much irrespective of what's going on in my life.
It was an interesting experiment but I didn't see the point carrying on doing it long term.