Never does a home improver feel so foolish as when he or she makes a mistake and loses money in the process. Trust us, we know. The staffers at This Old House, in our zeal to make our homes a better place, have fallen prey to impulse buying, overspending, mismeasuring, and plain old paying someone else to clean up the mess—the kinds of things that shouldn't happen to anyone, let alone a valued reader. So, to help all our friends avoid the red face and the empty wallet, we humbly offer just a few of the lessons we've learned the hard way. Read on to see how not to let the cost of home maintenance get the better of you.