Truer words have never been spoken...
What if everything that you understood about yourself was wrong including your most deeply held beliefs? What if what you thought about your friends was shaped by your collective experiences together - the pack mentality - and not by who anyone actually is? Perception is the filter through which we experience reality. It is reality in its cruelest form. However that filter doesn't always show us a clear or accurate picture. That filter can distort or diffuse. Reality, on the other hand, is inherently neutral and optically clear. It is our perception that shapes it and distorts and assigns it meaning when we view it through the filter of our life experiences. Essentially there is no such thing as reality, only the perception of it.
It is our confirmation bias - we look for evidence that supports our belief and we disregard that which doesn't. By the same token, we are what others perceive us to be. If I choose to go out wearing red lipstick and a low cut matching red top, I might be perceived as being a vixen, or a slut. It doesn't matter if I just like the color red, the reality is, that is what people might think and if they think it, chances are someone else thinks it. Perception is reality: to them, that is who I am regardless of whether it's true or not.
So what if you grew up with someone and you assign that person the title of best friend. That is how you perceive them. They are your best friend and therefore that is real. As you both evolve or devolve, what if one or both of you realize that you have nothing in common with the other person and your lives are going in completely different directions? We reduce our cognitive dissonance by convincing ourselves that no one could be a better friend to us than this person because we've know them all of our lives, and thus we cling onto our reality and don't let a silly thing like perception change it.
What if we alter our reality with drugs or alcohol? Does that change our perception? I'd offer that it does. Drugs and alcohol are often a shared experience and the ritual of it becomes part of our collective unconscious. Drugs, in particular, can permanently alter your brain. The way your synapses fire. The way your neural pathways form. The perception of our 'drinking buddies' as our true friends is real. Have a couple of beers every night because everyone else does? All fun and games until you become an alcoholic. It doesn't matter if, over time, we want to do more that go out and get fucked up. If everyone in our peer group wants to do it then it must be what we want to do. Saying no risks expulsion from the group - social death to the young and sweet freedom to the old. Then our perception of who our friends are changes. That is a little too much for some people to handle. So they play along and they get dragged down into someone else's reality.
At some point, you have to stop living down there and look up. On a clear day, you can see reality. Life begins in that moment.