“Now is the time to get serious about living your ideals. How long can you afford to put off who you really want to be? Your nobler self cannot wait any longer. Put your principles into practice – now. Stop the excuses and the procrastination. This is your life! You aren’t a child anymore. The sooner you set yourself to your spiritual program, the happier you will be. The longer you wait, the more you’ll be vulnerable to mediocrity and feel filled with shame and regret, because you know you are capable of better. From this instant on, vow to stop disappointing yourself. Separate yourself from the mob. Decide to be extraordinary and do what you need to do – now.”
Epictetus

Seneca said, “The problem is not that we have such a short space of time, but that we waste so much of it. Life is long enough, and it has been given in sufficiently generous measure to allow the accomplishment of the very greatest things if the whole of it is well-invested.”

Waste no more time arguing what a good man should be. Be one.
Marcus Aurelius

“It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat.”
-Theodore Roosevelt