Chaza"l say; "Repent one day before you die" which is explained to mean that one should repent every day, since no one knows when his day will come.
When surrounded by all the illusionary desires of this world, it is easy to lose sight of our priorities in life. But one way to stay strong is to keep asking ourselves "Will I be alive tomorrow? Am I satisfied with my spiritual progress, that if I should be called to meet my maker now I would not be ashamed?"
If we are at least trying to be better each day, we will not need to feel such shame when we are called back to heaven. But if we are negligent, G-d forbid, in guarding our eyes and aren't even trying to purify ourselves, what terrible shame we will feel!
So don't leave it for tomorrow. Start striving for purity today. Who knows what tomorrow will bring?