What does the speaker in this poem say will happen to "thy thoughts, when thou art gone"?

Music, When Soft Voices Die (To--)

by Percy Bysshe Shelley

Music, when soft voices die,

Vibrates in the memory.--

Odors, when sweet violets sicken,

Live within the sense they quicken.--

Rose leaves, when the rose is dead,

Are heaped for the beloved's bed--

And so thy thoughts, when thou art gone,

Love itself shall slumber on.