Source: Pagal Harnath letters
To worship Lord will be difficult once the time is allowed to pass. You will never be able to get any water even if you try million times, unless you store it during the rains. For men, their youth is the rainy season. What do you expect to achieve in the old age, once you allow this happy time to pass by? So I tell you this the proper time to meditate upon the Lord. Nurture carefully the roots of love that have sprouted in youth. All your efforts will be crowned with success in time and then you will be able to withstand heat of the summer as well as to give relief to the wayfarers.
If on the other hand, the roots shrivel up due to heat, million rainy seasons will not be sufficient to do them any good. Therefore make proper use of this priceless time with the greatest of care and judgement. You wasted your youth million times before. If you have shaken off your sleep and regained sobriety this time, make the best use of your youth by worshipping the Lord and repeating His names. Brothers, you are now endowed with evanescent gift of youth, make the best use of it and gratify yourselves. Youth never returns once its lost. This is like the mid-day Sun, a single minute after mid-day and it will gradually go down from the zenith till it is lost.
Please check these: Excerpts from a discourse by our Sri Sri Muralidhara Swamiji