This is an excellent article that can be read in its entirety at the Alzheimer's Reading Room.
"When guilt catches up with me, I am on the bike path above the creek, ducks swimming along beside me. Guilt rolls off our backs like you know what. Alone at last, I walk at my own pace. Fast. Fast is what Ben can no longer do -- and fast is slow compared with the woman coming toward me as I near the marsh. She is wearing shorts and earphones. She smiles and I smile back. What a good idea this is, walking out in the sun and cold. What could produce better clarity? I don't have to work it out the first day. I don't have to do it right the first time."