Live in the present, not the future, and certainly not the past. Living in present we are able to free our mind from uncertainty. Never spend all the time regretting events that have already passed or worrying about what may happen. Accept that you can't change the past, but that you have a large amount of control over what you do in the present, which will influence your future. Don't put off for tomorrow what you can do today. If you live every day as if it might be your last, it will be much more fulfilling and allow you to focus on what matters.