I think Ettsen is crying because he held out for so long, not accepting the OG princess' ""advances"" and now that it's over, he's like "Wow, was all that suffering, this drawn out game of cat and mouse, tip toeing around the Princess, fearing for Yuriel's life and mine, all of that is over so soon?". Like, this enormous ball of stress, pride and duty is gone, not after a ferocious battle but overnight?