sounds like he's at a bar and hes quite intoxicated, still drinking even though hes feeling sick
the yellow horse is a yellow taxi cab, one is waiting outside (like taxis wait outside bars)
he rides home feeling heartbroken and sick, hoping it will be over soon.
hes remembering the night before he was drunk, possibly gate crashing a party and before he had messed his shirt and possibly remembering a girl he has just broken up with, remembering being home with her in bed and not in a smoky bar.
sounds like he's at a bar and hes quite intoxicated, still drinking even though hes feeling sick
the yellow horse is a yellow taxi cab, one is waiting outside (like taxis wait outside bars)
he rides home feeling heartbroken and sick, hoping it will be over soon.
hes remembering the night before he was drunk, possibly gate crashing a party and before he had messed his shirt and possibly remembering a girl he has just broken up with, remembering being home with her in bed and not in a smoky bar.