Since adolescence, I've been trying to figure this one out. This one is a doozy because it has almost broken me a time or two, but here is what I've got so far...
...friends are the people who don't control. Who have high expectations of you, but don't guilt or punish you when you make mistakes. Who inspire and support you, not belittle and drain. They give before taking. They celebrate in your successes and are not jealous or resentful. They delight in your happiness and do not make you feel less than them. They are not mean and curt to you just to make themselves feel better. Friends do not make you feel paranoid and insecure. They appreciate your idiosyncrasies. They are quality, not quantity. They are open, caring, thoughtful. They have firm boundaries and are assertive in their opinions and beliefs, but they are not dismissive, condescending, or cruel.
Friends know you. They work to have a deeper understanding of what makes you, you. They make you a part of their world, but they don't rely on and suffocate you. They share their joys along with their sorrows. If it's only ever the latter, that's not a friend. They don't treat you like an inconvenience or a consolation prize. They value your company, your words. They respectfully challenge you. You don't need to do anything, it's just natural. Friendship shouldn't be hard, and it shouldn't have to be declared. It should feel like your soul was meant to know this person for whatever reason. They are protective, but not intrusive. It is actions, not words (for some reason, this was the hardest for me to learn).
Friendship is the long-term. It is the constant. It is refreshing. You feel better after time spent together, and that time is spent sharing ideas, hobbies, beliefs, insight, feelings... not just gossiping and tearing others down. Be the example of what you expect in a friendship, and do not settle. This might mean a little loneliness, yes. And yes, friends make life richer, but not when they're bad, destructive friends. Friends want to grow with you, experience new adventures with you, not just remain stagnant or living for past happenings. Friends are interested and curious about your life, and value loyalty and fidelity. Friends are forgiving, but not forgetful.
Good friends are the exception, not the rule. And sometimes friendships go through seasons, changing and fading. That's okay too. We learn what we can from the time spent and apply it to the next experience. Friendship is not perfect because people are not perfect but you look at the big picture and you focus on the people who actually bring value to this world, to your world.
And know this, that even the people outside of your world deserve respect and well wishes, even when you want to do the opposite. Because you should never regret being kind. And sometimes you'll still be hurt regardless, but in that comes greater understanding of the human condition, and growth in character.
I love you always,