"Why did you have to wait until I resigned to let me know you appreciated me?"
A manager in one of my leadership workshops recounted the sad story of how one of her team members reacted to the heartfelt speech she had made recognizing his contributions on his last day with the company.
Unfortunately, this scenario of "too little too late" is far from uncommon. In the book How Full is Your Bucket? Tom Rath and Donald O. Clifton report that the number one reason people leave their jobs is because they "do not feel appreciated."
Despite research showing that employees who receive regular praise and recognition are more engaged - leading them to be more productive and more likely to stay with the organization, among other benefits - more than two thirds feel their efforts are not appreciated. 
Why is recognition painfully absent in the lives of so many people? This may have something to do with the natural "negativity bias" in our brains. 
Dr. Rick Hanson says "the brain is like Velcro for negative experiences, but Teflon for positive ones" because in evolutionary terms it was of utmost importance that our ancestors notice, react to and remember things that could threaten their survival. While nowadays most of us do not need to worry about being attacked by a large carnivore on a daily basis, we still carry the same negative, threat-focused hardwiring in our brains.
This may explain why so many people find it easier to look for and respond to problems than to notice and react to the positive things that occur. Dr. Hanson writes, "In your own mind, what do you usually think about at the end of the day? The fifty things that went right, or the one that went wrong? Like the guy who cut you off in traffic, what you wish you had said differently to a co-worker, or . . ."
The good news is that you can start to change this negativity bias in your brain simply by making an effort to look for the good each day and by taking a moment to savor whatever you notice. The next step then is to share your appreciation with others.
To have the most impact, make sure your praise is:
- Positive - focus on the good to let people know they're appreciated
- Sincere - only say it if you mean it
- Specific - say exactly what they did that was so good so that they can do it again
- Frequent - people need regular (at least weekly) recognition to feel fulfilled
- Timely - the sooner the better as it's easier for people to learn from fresh memories.
In case you have any remaining reservations around sharing your appreciation, allow me to address the most common objections I hear:
- Don't have time? - Sharing praise can be done in a matter of seconds.
- Don't have a recognition budget? - Letting someone know you appreciate them is free.
- Don't feel comfortable praising someone in person? - Write your appreciation down and send him/her the note.
- Worried your praise will cause the recipient of your kind words to become complacent? - Research has shown that unexpected, non-monetary recognition is among the most motivating of rewards. 
So don't wait until it's too late. The next time someone does something you appreciate, Mention It.