A stitch in time saves nine.
An ounce of prevention is worth a pound of cure.
These old adages refer to maintenance. Better to maintain anything before it breaks and requires an overhaul or a new part. This applies both to inanimate objects and animate ones.
Obvious examples are checking the air pressure in your tires and getting oil changes when needed for your car. If you don't, the dreaded "Check Engine" message lights up on the dash followed by the inevitable bill to the mechanic.
Checking our blood pressure and getting blood drawn to get a picture of the healthy functioning of our bodies is similar. Except there is no "Check Engine" message, but rather a panicked call to 911.