Do not deride yourself that you have lapsed into a moment of depression.
A chink in your armor of positive thinking does not mean you have failed.
Things are not as bad as they seem, and you are not bad as think you are.
Forgive yourself before you forgive others.
Smile at the lapse, laugh even, draw your strength from your laughter, and plod on.
Your goal is not to be perfect, nor to do perfect things. They are secondary.
Your goal is to first fall in love with yourself, and then share the love with the world.