You may feel this way because of the way you have been treated in the past. A pattern has been set in your mind and you have to break it. Do things to help yourself. Acknowledge your accomplishments, Practice talking positively about yourself - out loud, give back to your community or friends and family by doing things for others - you'll feel good about it, write down things your grateful for - try to do that every day to remind you of the positive parts in your life. You can recondition yourself. You can break this cycle.