“Do you start with good intentions but soon lose heart when you don’t see results, want to know how stay motivated & achieve your goals? “

Yep, that's totally right, lifestyle changes make the biggest difference.
I also think you have to find the exercise/sport that works for you. I can't stand gyms myself, but enjoy a bit of footie regularly and tennis in the summer to keep me active, and the odd half marathon. Being outdoors makes a real difference I think, but I also agree that having a focus and target really helps and gives you a sense of achievement when you reach those targets.