Turn a bad situation into a good one.
Historically, the people in this world who achieved the most success were also those who overcame great obstacles. Your infirmities actually help you greatly—Beethoven probably composed such beautiful music because he was deaf, Helen Keller probably embarked on a brilliant career due to her blindness and deafness, and Leo Tolstoy probably wrote such an immortal novel because of all the torture he went through in his life. The most beautiful things are born out of pain, by those who care enough to try.
Do not engage in self-pity.
There will always be a reason for you to curl up and pity yourself for the tragic situation you are stuck in, but if you do that, you will never achieve anything in your life.
Always work on turning lemons into lemonade.
Even if you cannot turn a negative situation into a positive one, simply trying will help you stay in a positive mindset. This will, in turn, give you the motivation to keep trying.