At my age, this has happened more times than I care to admit. With some people, it’s like no time passed at all, and everything is great.
With others, it has become very evident why we lost touch.
I haven’t discovered a way of seeing who is what type without just trying to reconnect and seeing what happens.
I don’t really notice that I’m thirsty, so I used to go full work days without drinking anything other than a glass of water that my colleague gave me at lunch, then feeling strangely tired when going home.
The end result was a kidney stone. After that painful experience, I always have a bottle of water in my office, and make sure that I drink one bottle before lunch and another in the afternoon.
On days off from work, I still forget to drink, because I don’t have my water bottle there to remind me.