苦心孤詣

to make painstaking efforts (idiom); after much trouble / to work hard at sth

bitter / hardship / pain / to suffer / to bring suffering to / painstakingly

painstaking effort / to take a lot of trouble / laborious at pains

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]

lone / lonely

to go (to visit a superior) / one's current attainment in learning or art