Fix the Roof While the Sun is Still Shining

The best time to fix the roof is when the sun is shining.

Be proactive.

Don't wait until you're unhealthy to start trying to get healthy.

Don't wait until you're chronically weak before taking strength training seriously. 

Take the trash out to the bin before it's over flowing.

You get the point. Do the work while it's still convenient. If you wait until it's too late, or inconvenient, you're going to be miserable.