When I was young in my teens and early 20's I was so open and trusting to the point of being gullible really. I also had a tendency to really put other people on a pedestal and think they were so perfect and wish I could be like them. Unfortunately this meant that people would often try to take advantage of me, hurt me and I did some pretty dumb things.
Now I'm in my early 40's and I am so much more guarded than I used to be, I am extremely private and probably quite hard to get to know. I have really strong boundaries now and tend to keep people at arms length until I know how much I can trust them if at all. I do have a DH who I've been with now for 20 years and he has never let me down and I have a few family and friends I know I can rely on.
In many ways now that I am older and have had more experience of life I think in many ways I am more sensitive and compassionate than I was when I was younger. I appreciate the complexity of life and am less black and white in my thinking but I am also less likely to get involved and probably prioritise my own wellbeing over helping a random person.
I think of things like when I was younger I tried to help a homeless man who sat outside my work and it didn't end well for me or volunteering which just ended in me getting exploited or friends who just saw me as a resource to use up and discard or same with people who wanted to do the same in the work place.
I wonder if this is the same for everyone, I suppose it is for many.