Answer:
To abandon is to completely forget about something, like
"i completely abandoned the idea of getting that shirt".
To leave is to go away, and you don't just say
"i completely left the idea of getting that shirt."
that just sounds weird.
Leave can simply mean to depart.
My train will leave the station at 3:30pm
sounds better than
My train will abandon the station at 3:30 pm.
See the difference? If not, comment and ask.
