Preserve things that are worth preserving: try not to let something go bad, or become unusable, through neglect, carelessness or inattention.
This has a corollary helping tool that Bill has been training me over the years to apply more often:
Try not to set yourself up for trouble.
If you see something and think "That's an accident waiting to happen," change it. Don't walk out of the room and leave something that will be ruined if left that way for too long (something on the stove; an iron skillet soaking in water, etc.) and don't count on your memory when it would take only a moment to fix something right now (close the bread bag as soon as you take the bread out; rinse out the crystal so it's not left in the sink to be broken by someone who doesn't know it's there; move shoes away from the bottom of the stairs, etc.). Set up tracking systems so you know when batteries and oil were last changed, water heater last flushed out, etc., (or do them on a particular schedule) so you are not simply depending on your memory to help you take care of things that need regular maintenance.