The phrase "to see the difference for someone" means that you can recognize and understand an improvement or change that has occurred in someone's situation or behavior. Full definition
Sentences with «to see the difference for someone»
I just don't do them anymore because I really didn't see a difference for me. (trainingscience.net)
After 30 days I stopped using this regularly, and I didn't see any differences for my skin. (berriesinthesnow.com)
Nintendo actually uploaded two videos, one of them comparing 150cc to 200cc so that players can really see the difference for themselves. (perfectly-nintendo.com)