You'll seldom experience regret for anything that you've done. It is what you haven't done that will torment you. The message, therefore, is clear. Do it! Develop an appreciation for the present moment. Seize every second of your life and savor it. Value your present moments. Using them up in any self-defeating ways means you've lost them forever.
There is no man, however wise, who has not at some period of his youth said things, or lived in a way the consciousness of which is so unpleasant to him in later life that he would gladly, if he could, expunge it from his memory.