An app may or may not succeed despite your best efforts. Your physical goals will show positive rewards, and I do recommend some "positive definite" activities to keep you from the anxiety and depression.

I am retired now, but things like photography and piano always rewarded my efforts. So did raising a wonderful daughter. She got an honors psych degree and always recommends a therapist. I tell her that I'm too old to fix!

Your programming efforts are the means, but also an end. You'll grow from them, and even if your app is not a "killer" app, your work will find a use. I had a wild variety of jobs and always had to learn new things for the next one. In the process, I found that "good homework always pays off" eventually.

I hope that your efforts bring forth your desired result, but be prepared to be surprised if you succeed in unexpected ways.

Health is wealth, too.