I keep forgetting I'm partly blind.

Jack Kornfield tells this story from Alan Wallace in his book The Art of Forgiveness, Lovingkindness, and Peace:

Imagine walking along a sidewalk with your arms full of groceries, and someone roughly bumps into you so that you fall and your groceries are strewn over the ground.  As you rise up from the puddle of broken eggs and tomato juice, you are ready to shout out, "You idiot!  What's wrong with you?  Are you blind?"  But just before you can catch your breath to speak, you see that the person who bumped into you actually is blind.  He, too, is sprawled in the spilled groceries, and your anger vanishes in an instant, to be replaced by sympathetic concern:  "Are you hurt?  Can I help you up?"  Our situation is like that.  When we clearly realize that the source of disharmony and misery in the world is ignorance, we can open the door of wisdom and compassion.