Yes, I think these feelings are normal, perhaps especially after 30 years in the same place.
I broke down in tears when DH first suggested moving after a similar length of time. However, I soon saw the advantages and am happy in our new home.
I hope and feel sure you will be too.
It is all right to have these private moments and you obviously have managed to wish the young couple you are selling to all the best in their new home, so pat yourself on the back.
Once you move away, resist the temptation to go back to your old area on a visit. Eight years after moving I still don't want to visit my old neighbourhood.
A word of advice: you may find yourself dreaming at night that you are back in your old home, either living there or sneaking in to look. I do, and have decided that these dreams are just part of having been attached to the place and nothing to bother about.