1) You don't realize that it's not about what you want, but what you need. Everyone wants Prince Charming, but it may not be Prince Charming who is the most compatible with you. Aim for someone who compliments your personality, and stop having a set criteria.
2) You don't realize that you also have to make an effort in relationships. Get off your high horse and realize that maybe certain things about you need to be changed a little. To help, check out my post on what you should and shouldn't change about yourself.
3) You overthink every single little thing. 1- it's REALLY annoying to be with someone like that and 2- you're probably sabotaging most of your relationships with this...over nothing.
4) You keep going after the same kinds of people. Change it up. Look outside of your comfort zone, and re-read #1.
5) You "know" exactly what you want. Always keep an open mind. If you're always searching for "what you want" exactly, you'll probably miss out on the best thing that is right in front of you.
6) You're afraid you're going to "settle". I'm not really sure why the word "settle" now holds a negative meaning. To settle means to adopt a more steady or secure style of life, and if you're happy in your relationship, and you're in fact "settling down for someone", it's actually a great thing, so stop thinking otherwise.
7) You think you're going to be tied down. The only way you'll feel tied down is if you're in the wrong relationship. Being in a good, healthy relationship will never make you feel this way, so focus on finding a compatible partner rather than thinking you'll lose your freedom.
8) You're always thinking that you could get someone better. A boyfriend or girlfriend is not like an iPhone. You can't just go get the next "better" version. Newsflash: there will always be something "wrong" with your partner. No one is perfect, start realizing that.
9) You think that because you're young you shouldn't take your relationships seriously. Well then why should anyone commit to you...?
10) You have unrealistic expectations. Life is not a f***ing romance movie. Throw away your expectations, because you will be disappointed, unhappy, and single for the rest of your life. The moment you will stop having unrealistic expectations will be the moment you will realize what REAL love is about.