We all want to be told that our work is important. That what we're doing is making a difference in the world, even if it's small. We look to our friends, family, coworkers and employers for this feeling of necessity.
Some days, people will tell you how much your work has meant to them. That you have changed their life somehow; and it will feel pretty good. But if another's testimony truly validated our work, why do we constantly have the need for more people to acknowledge us? Do we not believe them?
The problem for those seeking validation is that even if everyone in the world told you your work is important, you would wake up tomorrow and find another reason to question it. On the edge of paranoia, needing validation for your own work is an endless loop. Maybe someone else will praise you, maybe they won't.
You must first learn to be satisfied with your own accomplishments. And the more value you see in yourself, the less you will need validation from others.