We recently discussed the real hazards of stamping “lifetime warranty” on your products. A close corollary to that is promising “satisfaction guaranteed” on your professional services.

You might make that offer because you are proud of the quality of your services — so confident that your work will be above reproach that you are implicitly claiming that you’ll redo the work or refund to make the customer happy.

Think about that outrageous promise. How can you possibly guarantee another’s happiness? Why hold yourself hostage to that? Do you think it impossible that at some point — probably nearer than you think — someone will ask you to redo your work for free or demand a refund, even on the materials you purchased?

First, there are perennially dissatisfied people in this world. Nothing makes them happy because it is their personality to criticize, be disappointed, and generally find fault with everyone and everything. You have probably met at least one person like this in your lifetime. That is exactly the kind of person who will ask you to redo your work over and over and over again, dangling your promise of “satisfaction guaranteed,” while you continue to shell out more money for supplies.

Eventually, you’ll get so angry with this unhappy person that you’re willing to give a refund just to be able to walk away from this sour relationship without any guilt. Yes, those kinds of people are definitely out there — and they will find you and test your promise. Guaranteed.

What about the people who simply change their mind? “Yes, I know I picked this brown paint, but I didn’t realize it was just so dark. I am not satisfied so please repaint for free with a different color. You guaranteed satisfaction, and I am definitely not satisfied.” Believe me, that will happen.

A professional painter told me about just such an occurrence. The client picked the paint, and when the deck was completely painted, complained he didn’t like the color and demanded a complimentary repainting, blaming the painter for not overriding his color choice. Fortunately, the painter had listed in the contract that the client would choose and supply the paint; they parted ways with the customer nevertheless feeling that he’d been wronged but without legal recourse.

Then there’s another type of customer who will abuse your promise of guaranteed satisfaction. There are people who are so sensitive and malleable to others’ opinions that they transform from satisfied to dissatisfied in one day.

One handyman’s customer was absolutely delighted with the work he had performed for her, gushing about how perfect it was and that she would recommend his services to everyone she knew. Well, that was her opinion until the next day, when her family came by and told her she was stupid for being satisfied with the work and that she should have hired a friend of the family who would have done a better job.

Suddenly, this satisfied customer was anything but and demanded her money back. Instead of recommending him to her friends, she was instead going to tell everyone she knew about his lousy workmanship. What happened? Family happened.

So what is the point of promising satisfaction — to prove that you stand by your workmanship? Don’t confuse the quality of your workmanship with customers’ being satisfied with their decisions — or their lack of specificity. “Yes, I did say that I wanted a new electrical outlet by the sink, but I wanted it three inches higher and to the right; I didn’t know you were going to put it right there; I don’t like it there. I am not happy. Would you please redo it and install it higher up.”

How can you avoid these very real scenarios?

As with anything else in dealing with the volatile, fickle public, put it in writing. Specify the terms — when you’ll start, estimated time to finish, payments. Specify the materials you’ll be using, such as “customer-provided paint” or “.5 inch x2 inch x12 foot pretreated redwood.” Specify the workmanship, for example, installed per electrical code XYZ.”

The idea is to quantify observable and verifiable attributes of the finished project without depending on an ambiguous variable like a stranger’s state of being.

You can present testimonials and references for past work, but it is a costly and frustrating mistake to agree to make someone happy. You can’t make anyone happy. Sometimes you can’t even make yourself happy! So why would you give that power to a stranger?