It sounds like 18th avenue was a dark part of his past, when he did a lot of things wrong in his life. Its hard to go back there, and its a painful memory "to repeat the words That I used to use only yesterday". Its also hard on him to believe he ever did the things he did there ("I tried to remember what I thought And what I used to say "), and the people he remembers from the 18th avenue are all empty reminders of his past now.
It sounds like 18th avenue was a dark part of his past, when he did a lot of things wrong in his life. Its hard to go back there, and its a painful memory "to repeat the words That I used to use only yesterday". Its also hard on him to believe he ever did the things he did there ("I tried to remember what I thought And what I used to say "), and the people he remembers from the 18th avenue are all empty reminders of his past now.