What I mean by this is that we look for people "lower" than us, or more needy of us, so that it makes us feel we are totally in control. But in truth our insecurity is in control, because instead of dealing with it and overcoming it, we are only feeding it, growing and nurturing it to become something of a phobia. We need to realise, its all a state of the mind, and the mind is such a powerful tool. This is not about fighting, and winning the war of your insecurity, this is about being intelligent enough to deal with the problem after you have realised it.
How to deal with it?
It depends on what your insecure about. It could be looks, it could be lack of knowledge or intellect, it could be that I think my partner will get bored of me, its all a state of the mind, and they all require simple communication, with yourself and with your partner.
Talk to them, ask them what they love to talk about, ask them how they love to see you dressed, ask them about what they want, and then work on it. Maybe you will keep failing at it, for example, I am not great at talking politics, but the more I try to talk about it, the more informed I will become, the closer I will become to developing my own ideas and feelings about it, and even my own opinions, and strategies. Its a step by step process, one which you may fail at some steps and seem a bit dumb, but don't take it so seriously, its important to be able to laugh at yourself and your own mistakes, and have fun in teaching each other, and don't allow the other person to feel stupid, we are what we are at the end of the day, we are all learning here and a sense of humour goes a long way in relationships, marriage should be fun, lets not forget that, because we are on this journey together.
We always tend to imagine the worst in our heads, especially us women, most likely its not even like that. We over think things and play things up so much in our heads that it becomes a mini drama. But in fact, this thing that you find such a massive problem, really isn't so massive. Find something else in the relationship to concentrate on, something you know your good at, making people laugh, informing them of interesting information, cooking, and physiologically your confidence with naturally increase, and once you have reached this level, you will start to naturally feel confident in other things too, allow it time, to take its own course, step by step.
Running away from marriage is not the answer, not for long term anyway.
Trying again and working on it with your partner is. We are all scared of failing, but if we don't try then neither will we succeed. Marriage is about teamwork, friendship, understanding, you should want to help each other be better partners, most importantly, you should allow your partner to help you, we just need to try, because in effect this makes us better slaves of Allah.
And Allah knows best.