people change?!

Something rare and strange happened to me: in one hour i met 2 persons i didn't see for almost 10 years.
the first is a girl i used to like very much and believe she's really a very good person with the open personality that makes her deal with everyone with a good spirit
the second is a guy i used to dislike a lot, and really i said after he left the country "Egypt now is a better place"
the difference between the 2 meetings was minutes
at first i met the guy, he was standing there and called my name, i looked to see who is calling and then i only said the following:
- OHHHH, u r here, u r back !!!!!!!!!!
- thank god u remember me
- i remember u, welcome back
-thank you
- well .... welcome back, excuse me, BYE
and i left
what happened exactly was that when i saw him a button was pressed in my mind "open the old box of dislike"
after half an hour, i saw this girl coming toward me, i smiled i laughed
i hugged her and said i'm very glad for this opportunity to see u again
we exchange our phone numbers, we talked about nothing important really
just chatting, this time the button in my head press the "like, love box"
honestly i was talking to her as if i see her everyday
it was a very good relief feeling to talk to her again
after a while a friend came to me asking me why i'm not talking to the guy
so i said: are u kidding!! i never liked this guy, anyway i said welcome back
- COME ON, it's been 10 years , people change
and he left me feeling bad about my self
he was absolutely right and i was definitely wrong
PEOPLE CHANGE
for the most the change is for worse but from time to time people may develop to be better humans
i was stupid, i didn't deal with the parameter of "time" correctly, my good friend may change to be a bad person and the bad guy may become a better person
but i used my old feelings to judge them both,
i use my previous experience to judge the future always and it's wrong
but again, how i neglect what is established inside me as facts (this person is good because ...., or this person is bad because .....)
if we set our personal experience aside when judging people, then what we should use? apparel?
should i start making new experience with every person i didn't see for longtime because "people change"?
the essence of anyone will never change by time but it only be more visible, and had more effect in his/her actions, i believe
but am i wrong?
are people really change and deserves a chance to rejudge? are our memories and experience the best judge?
what do u think?