Failure to Thrive means that a person is not growing, developing, or doing well the way that is expected for someone at their age. It usually means that a child is not growing at the expected rate, but it can also describe adults who do not seem to be reaching their full potential. Failure to Thrive can happen for many reasons like not getting enough nutrition, not getting enough exercise, or not having a positive environment to grow, learn, and be happy in.