Most Helpful Guy
Both of those are real possibilities (that they weren't the right ones, and that you needed to change/grow a little).
I have been in a couple very serious relationships myself, and obviously they didn't work out. I did change as a result of them, but it's not like I made a conscious decision to do so. It was more like a growth of character, I guess.
Anyway, it's unlikely that you've got anything majorly wrong with you. What's more likely is that these were just the wrong guys at the wrong time.
Most Helpful Girl
Hm, what were the arguments about, if you don't mind me asking?
Sometimes when people are in a relationship for so long, they start to get anxious, or bored, or who knows what... I know it's tough to have a long-term relationship come to an end, but don't place the blame all on yourself. Obviously the relationships went well for a while, but then something changed somewhere along the way... it's up to you to figure out what that is. Did the spark die? Did the two of you realize you had different views on where you wanted the relationship to go?
For whatever reason, your compatibility faltered, and the two of you were unable or unwilling to work on it. I'm sorry to hear things didn't work out, but hopefully you can still take something from this, and have a more successful relationship in the future.