Like attracts like. This is one of the most important lessons I've ever learned in life. Spring cleaning is usually a time to clean out your house--I'm currently organizing my crib--but you should use this time to also clean out your personal life. Look at the five people you spend the most time with. Do they motivate and inspire you to be YOUR best?
There's nothing to leave or change a friendship. I know it's hard. You don't want to be mean or look like you've changed but in reality, if you want to be your best you need to surround yourself with the best. Here's a great article about outgrowing friends--and why that doesn't make you a terrible human being from the Art of Charm.