I've realized that friends can be more of a liability at work than a benifit. Most people know this and have mastered the art of being friendly while avoiding any deep emotional involvement. When I was younger I was hungry for that high school feeling too, but it's best to look for it in other places. Professionalism is the standard for a reason.

Some hypotheticals:

You make a friend at work. That friend gets fed up with their role and quits. Your morale takes a dive.

Friend at work starts to have performance issues. You get caught between supporting your friend or the team.

Friend at work is now your boss or is put in a position to manage or inspect your work.

Friend at work gets laid off.

You share some personal details with friend, personal details are then shared with others.

You office gossip with friend over drinks. It comes back to bite you.

It was and still is hard for me as well. I tend to get emotionally involved with whatever job I do and the people I work with and that sometimes creates friction with people who prefer a level of professional detachment (or just don't care).

Anyway: I recommend the book "Reinventing Organizations" for a look at how to create more human-friendly orgs and "Time to Think" for some powerful tactics to use at a team level.