Just keep trying! Remember that a person chooses whether or not they will like you from the minute they see you. First impressions are important! Also be GENUINE!!! A lot of job seekers are so busy writing out thank you cards and cover letters instead of being real. Work on being likable, which means you need to be vulnerable and honest. When I was hired at the hospital in my city I told the manager that I was kicked out of nursing school due to being sick... that I struggled with the idea of going back to a school that had made me withdrawal for missing TWO DAYS. Then I told her that I humbled myself and went back, because nothing was going to stop me from doing what I was meant to do. This made me vulnerable. She knew a secret, she knew something that could work against me.(No one wants to admit they got kicked out of nursing school!) Many people forget about this very important part of human interaction, to make a real connection with someone... you have to make yourself vulnerable.
So keep at it! Make sure you are not in a robotic rut of jumping through hoops, but that you are letting employers really get to know you, the real, honest, & raw you! : )