As soon as you stop advancing, as soon as you stop progressing, as soon as you cease to better yourself, cease to gain and grow, cease to transform yourself, you truly become old, that is to say, you go downhill towards disintegration.
There are young people, who are old and there are old people who are young. If you carry in you this flame for progress and transformation, if you are ready to leave everything behind you so that you may advance with an alert step, if you are always open to a new progress, a new improvement, a new transformation, then you are eternally, Young.
But if you sit back satisfied with what has been accomplished, if you have the feeling that you have reached your goal and you have nothing left to do but enjoy the fruit of your efforts, then already more than half of your body is in the tomb: it is decrepitude and the true death.
~ Sri Aurobindo