Know when it's time to move on and learn from mistakes.
This is hard. When you create something, you want it to be the best. You want everyone to see how great it is and love it as much as you do. When you don't get the response that you want, you need to choose if you keep going on with it or close it. You should take a look at the result. If you don't see anything good coming out of it, then you should close it and do something else. Take the loss and move on. Start something better.
You should give it some times before you close it. If you planned it on a year, then after 3 months you should see if it needs some changes. You should not wait until the end of the year if you don't get any result. If you did put lots of work in promoting it and it didn't make you any money, then you should think about closing that project.
Don't give up! Greatness is not a mater of luck. It's a mater of hard work.
Learn from your mistakes.