Yeah I know what you mean about the drop.
I've made peace with that by thinking a lot about biology and natural selection.
As you say the person who gave you that advice was: 'someone who claimed they were "trying to be a friend."', which I think everyone on this board knows is different than someone who IS A FRIEND. (I'm feeling a little inspired now to make a thread "How friends act" just to make it easier to tell who is your friend and who is just another random person in your environment.)
In the 70s I took a personality test to help me determine what I wanted my major to be in college. The one question I remember was "Would you like to have a lot of friends, or just a few close friends." I remember being stuck on the question for a minute or so, because I had never considered that there could be a continuum from people I've never seen to close friends.
At close to 60 I realize what hard work it is to keep close friends, much less make new ones. The world has been confusing enough to me that it has become harder and harder to trust someone. I think I could ascribe that to modern American culture. I grew up with the thought "Never trust anyone over 30", which has morphed into "Never Trust anyone who is younger than 45 or older than 75.
When I visited with my father in senior assisted living I got the same feeling from the people I met ... the closer they were to my father's age the less they seemed to trust me, in the same way that we don't let people who are younger than 16 or so drive.
So I don't know that argument really cost you a friendship. What it did is help you define the amount you want to be friends with the person that told you to "Cheer up and count your blessings."
I know that before my son was 16 I used to enumerate our blessings and try to put them in perspective. Of course, the closer he got to adulthood, the harder it was for him to adopt my perspective that things would work out. Similarly, my father and I disagree on "What's Important." We completely disagree on how the future will unfold in the near term, although we do agree that we have both passed the halfway point for the time we can remain on earth. Where youth gave me joy, age has now given me shadenfreude.
Thanks for helping me remember this, and thanks for letting me share it.