It might be an old saying but I find the words valuable. One of the most frustrating things I deal with is people who promise things on a certain date or time - with specific information - and it just doesn't happen. They miss the deadline or forget the information. Or both.
Let's look at an example - the hard drive on my computer died not too long ago. I was doing data back-ups like a good girl, but they weren't scheduled daily. And when the CPU crashed, I had some work that had not yet been backed up. My computer guy was honest with me. He didn't know whether or not he could recover all my files. He said he would try. I couldn't really ask for more since I wasn't backing up the data daily.
Couple days later, he called and said it wasn't looking good and I should not get my hopes up. A few days after that, I got the call that he had recovered everything. I was thrilled!
This is a classic example of under promise (i.e. "don't get your hopes up") and over deliver (aka "recovered everything"). If he had said, no worries...I can get the data restored and he didn't, then I would have been incredibly disappointed. Because he got my hopes up. And, it might have effected whether or not I believe his claims in the future.
Another example we're all familiar with is the proverbial "sandbagging" the budget. I have on many occasions understated revenue in the budget and overstated expenses. Why? Because it's easier to tell people the team made more or spent less than what was expected. The expectation is to meet the budget. If you don't, there might come a moment when you have to explain to folks that you didn't meet the revenue goal or properly manage expenses.
Some folks might call sandbagging the budget a game, but the reality is it happens. A lot. Because none of us like saying negative things like "Jane didn't sell enough." or "Bob spent too much on food at the meeting."
On the other hand, this doesn't mean that everything always turns out perfectly. We all have moments where something in our lives goes kablooey and we can't meet a deadline. Or we're thrown a curve ball and need to get additional information before sending in our report. But when we make a commitment to do something, the expectation is we will deliver. And if we can't, then the proper thing to do is let someone know. Communicate and renegotiate the deliverable.
Your customers will be delighted when you set realistic expectations, communicate regularly and create opportunities to exceed your promises. Besides, it will make your life a whole lot easier.
P.S. While this post is about exceeding expectations, I learned a valuable lesson about the importance of backing up computer data regularly. Listen to me. Do it. You don't want to recreate all of the stuff you have on your computer. Facing the prospect of having to possibly recreate even a few days worth of work convinced me.