How not to loose motivation about a side project?

Put it out into the wild as soon as possible, and get some users/customers. Then there always be some rush, that keeps you motivated.

You should always loose your motivation. That is no problem. Go wild!

Wait, did you mean "lose"?

I find it hard to lose motivation with beeminder (https://www.beeminder.com/) kicking my ass.

I used to have a lot of trouble.