Self image is how you see yourself and portray yourself to your world. We all have standards that are set. For example:- I might set a standard that I can get a job that pays up to $50,000/ year and that's the limit that I have in my head, and that's all what I would get, nothing less and nothing more. This number or standard could come from different resources ( a research I performed, the atmosphere around me, my friends, or what my teachers told me at school upon graduation), but it's a standard that I got used to and it's the result I will always get unless I change the way I think and alter that standard.
That's why self-image is key to your success and key to your life really. The standard you have set is engraved in your subconscious and it's what you'll automatically go for without even thinking.
There's the person that thinks "every month I need to get my bills paid", so every month, they do everything they can to just do that, and have nothing else in their bank account left until their next pay check, and that's a lot of people. Maybe they think they can't have more than just what their bills cost or maybe they don't feel worthy and deserving of having more money.
So be aware of your self image, make it a positive one. Remember the times you set your mind to do something and you accomplished it and that will give you the confidence to set higher standards for yourself and the confidence that you can achieve anything you want to achieve.
Remember that nothing is impossible and don't be afraid nor feel silly to have big dreams because that's your first step towards achieving them.