I agree with Sparkster that there is a butterfly effect to your actions but I think that applies more to the reactions your actions cause. Your present drives the way you are perceived in the future but it does not determine your future self. You can devolve into bad habits by repeating the same negative action but you can make a conscious decision to change. So I believe you can change your future, in the future. Or, I think it is more accurate to say you can change your present at any moment.