Stop making excuses for why they didn't call, didn't email you back, made you feel bad, or any other negative way they might have treated you. Don't ever think they are sitting around thinking about you--because, even if you are an incredible person, he/she is probably wrapped up in their own life. If they feel interested in you, they will take the initiative to contact you. Since they are not doing that, it means they are not interested in you.