How to see ghosts or surely bring them to you

 "They tell me I must wade into waters, where I will soon drown. Before I march in, I leave this on the shore for you. I pray you find it, sister, so you will know what was in my heart as I went under."

Khaled Hosseini: And the Mountains Echoed.

Some context: the quote is a  letter from a man to his sister, who was separated from him when they were both very young. By the time they finally meet again, his Alzheimer's has progressed to the point where he does not recognise her. It's simple but affecting.