The truth that you are living at the mercy of others need not tarnish your self-esteem. But you have to realize the self-esteem in its real sense. Within the loop of each activity in your day to day life and its result, apart from you, many others and things play important roles. Each one in the loop is a benefactor as well as a beneficiary of the act of mercy. It means, there is nothing like a permanent giver and permanent taker of mercy. In reality, giving and taking mercy is the wonderful glue that link individuals to form a society. Now connecting it to the opening two sentences, your self-esteem should be identified with your ability to give and take good things.
Practice it and make it a habit. Then the nature will make it sustainable by triggering necessary genetic engineering!