을지언정

Even if that were so

It concedes something and then insists on the other half regardless: even if the relationship did not work out, they may still have made good memories; even if you starve, keep your pride; even if there are disappointing parts. It is emphatic and bookish, at home in maxims and argument, and ordinary conversation would use 아도 or 어도 instead. The clause after it is the part the speaker actually means.

Register: bookish and rhetorical