It's just like seeing Juliet for the first time

 After witnessing Romeo and Juliet flirt during their first interaction at the Capulet feast during Act 1.5, I feel as if this was perfect timing for Romeo seeing he was lovesick over Rosaline before this interaction between him and Juliet when the two caught love at first sight.

For context, Throughout Act I, Romeo had been lovesick over this girl he loved named Rosaline, and he failed to win her over so he remained upset over this up until laying eyes on Juliet. As they both flirted after meeting each other, they conveyed a lot of emotion to each other despite them barely knowing things about each other, which leads me to believe this was a love at first sight trope.

While walking home from the party after this interaction with Juliet, I feel as if the one song he'd loop on his walk would be 'For the First Time' by Mac DeMarco. 

https://youtu.be/el1S8zbzIPE

The main lyrics he'd probably focus on would be "It's just like seeing her for the first time again" since it reminds him of the moment he saw Juliet, and how he caught feelings in that exact moment, or it reminds him of their first interaction where Romeo grabbed Juliet's hand and their conversation went on from there (Act 1 scene 5 sentence 104).

Another set of lines from the song that Juliet would come to mind to Romeo while listening to it is "Know she won't be gone forever / There are many times I feel it feels that way" since he might feel unsure if he'll see Juliet after this, knowing she's a supposed 'enemy' seeing she's a Capulet.