Friends are like flowers
Sometimes they're in season, other times they're impossible to track down ... or really expensive ... or making you sneeze ... or clashing with your color scheme. The point is, appreciate what your friend has contributed to your life in the past and recognize that there might be lulls in your relationship. That doesn't mean you have to throw away your half heart necklace. Be patient and you'll see that, in time, you'll return to equilibrium.
You won't always have the same priorities
You might be fixated on the SATs or landing your first job while your friend is consumed with her boyfriend's new haircut. Focus on being a good sounding board for your friend instead of trying to change their priorities. As long as they are willing to give your hang ups attention in return, they're doing their part.
Friends deserve the benefit of the doubt
If you're going to call someone you're friend, that means they traits that you value and respect. It does not mean that they are perfect or will always adhere to your BFF Checklist. They're going to mess up and offend you and disappoint your high expectations. It's fair to hold them accountable (sweeping things under the rug won't help), but take a pause before you react. It's likely they didn't mean to upset you and if they know they did, they're sorry, even if they feel too awkward to say it. So approach your tiffs with grace and understanding instead of accusations of malicious intent.
Your friends have friends that are not you
And that's allowed! For a long time I struggled with feeling like my friends all had other friends who they were closer with. But you've got to let that comparison crap go! Be confident in the value that you add to a friendship and don't get caught up in the pity party. You might be surprised how many of your friends feel the same way about you. If anything, let it motivate you to tell your friends how much they mean to you.
Never stop making friends
To be honest, I was never a big fan of the term BFF. For one, it puts a lot of pressure on a single person and for such a little word, it can do a lot to alienate the other friends in your "tribe". The older I get, the more I realize how important it is to have different types of friends. I treasure my childhood friends, but also realize that we've grown to be different people and can never know what it's like to only meet the adult version of ourselves. It can be nice to discover commonalities with new people and share laughs over long-buried stories. It's always been really valuable to make friends in the nonprofit world who know what it's like to build a business and can share valuable insight. The older you get, the harder it can be to put yourself out there and make space for new people, but I promise it is worth the extra effort!