The good thing is, we can all change. Your past does NOT define who you are. It doesn't matter what environment you grew up in, how people have treated you, how old you are, or how you are feeling right now. You may be YOUR OWN WORST ENEMY but you can become YOUR OWN BEST FRIEND. YOU are the ONLY one who can change your life.
Negativity CAN be changed into positivity. Bad habits CAN be changed into good habits.
You CAN become more confident and you CAN have better self-esteem. It takes 2 things - desire and commitment. First you need to have a deep desire for a better life, then you have to commit to actively and continually working every day, all the time, day after day to make positive changes until they become habit. It takes about 21 CONTINUOUS days to set a new habit. If you miss a day or two, don't get discouraged, you might have slipped back a bit, but you haven't lost all your hard work, just keep going.
Change is NOT easy, NOT quick and everyone won't have the same results in the same time period, but it is definitely worth your time and effort to create a better life. When you get impatient and don't see results fast enough, think about how long it took to create your situation and realize it will take at least as much time or probably longer, to make the situation better.
Just DON'T EVER GIVE UP, always KEEP TRYING!