The problem: Someone is gone and you suddenly can see the true values of that person.
We usually do criticize more than we esteem. And we often do contribute more to putting people off than motivating them. Only when they are gone we find more good characteristics then ever before.
The reason: The persons we see nearly every day or at least very often we do forget their transiency.
We tend to assume that people entering our life frequently will be there forever and even if not very comprehensible we do appreciate them less as "normal" they get for us. The negative effect that might occur then is reduced motivation and a reduced climate in the relationships to other people.
The solution: Imagine the missing of those people around you and get aware that it is not "normal".
Try to meet people each day for new appreciating their contributions to your work or life and thank them for their contribution and being. Get aware of the value they are for you and contribute to a good climate and motivation to be value for them also.