How regrettable.
I shouldn't have cancelled our plan, thinking that there would be a second time or third or fourth, like how waves continuously come to the shore.
I should've rode your motorcycle when you offered.
I should've ate ice cream with you when you asked to have one.
I should've took the pleasure of talking to you instead of being shy.
Ah, I guess there's no 'next time'.
How regrettable.