There's a difference between good change and bad change. If you notice yourself acting ways that are not in your nature, then you're probably with the wrong person. When you're with the right person, he/she will look to enhance what you already have and change you for the better.
If you allow emotions to dictate the relationship and don't stop to think about what you're doing, then chances are you won't know if you're ready to be committed or not. Investing in a healthy relationship is better for your soul. Too much sex and casual dating can leave internal scars. It leaves you with little trust in other people. Know what you're worth, and if you can't find an answer, then you need to find peace within yourself first.
Certain people come in your life to have you learn a lesson, whether it would be good or bad. Learn from the bad and merge it with the good. Use both your head and your heart. No one knows you better than yourself.