Our life in this world is not something that will continue until we succumb to some illness or accident. The only reason why we are still alive as long as we are is to enable us to perform more mitzvoth. Without mitzvoth existence would run out of energy; mitzvoth are truly a gift from G-d. If we delay, we'll be subjected to the accusations of the Satan that we don't deserve this opportunity. Don't provide more ammunition to the Satan. Don't let the mitzvah go stale in your hands.