I love the first line, very true. A dream is still nothing but a dream, no two dreams are the same... and for the person who did not dream it, it doesn't exist, they will never truly know how the dream felt and how it was almost real to you, it will be just another story to them.
The guitar string metaphor is nice. Once a guitar string is broken, it's easily fixed... a heart is a different story. It sometimes takes years to mend, and it's always harder to move forward to play a new love song.