| Quote #1
My friends forsake me like a memory lost;—(2)
A lost memory is pretty much gone for good. It's dead, and cannot really be recovered. The lines suggest that the speaker is already dead, and they foreshadow his death wish later in the poem.
| Quote #2
And yet I am, and live—like vapours tost (6)
Is he alive or dead? The speaker says he "is" and lives, but then immediately compares himself to "vapours." There's nothing really alive about vapor; it's thin, wispy, and practically invisible—like a ghost.
| Quote #3
Where there is neither sense of life or joys,
No "sense of life"? That sounds like death. A "vast shipwreck"? There's usually some death in a shipwreck. The speaker is surrounded by death, but death that wreaks havoc (a shipwreck is, well, a wreck!).