The next time a part-time friend asks why you don't call or text anymore, ask them when the last time they went out of their way to just check up on you, when the last time they thought of you and picked up the phone just to chat, or when was the last time they didn't just talk about themselves before finally getting around to asking about you. You are not a rug, stopped being walked on. Instead, throw on some boots and do the walking yourself.
This is how I roll and it makes my life so much easier. I recommend it to everyone. Know who your friends are and know who your aquaintances are and know who you call when you just need a fun distraction. Most importantly be the best friend you can be and don't worry if they don't reciprocate. That's not your problem.
Sometimes you can mean almost nothing to someone who means so much to you. It’s not pride – it’s self-respect. Don’t expect to see positive changes in your life if you surround yourself with negative people. Don’t give part-time people a full-time position in your life. Know your value and what you have to offer, and never settle for anything less than what you deserve. - via: http://www.marcandangel.com/2012/05/23/14-rules-for-being-you/