Heavily.
Having great weight; ponderous; hard to lift, bear, or suffer; dejected: sluggish.
Heavyness.
" No, you are not to blame this time, Umbelazi," replied the King, with a heavy sigh. – Child of Storm by H. Rider Haggard
My heart was very heavy. – Ismailia by Samuel W. Baker
I like the idea of him having 'a heavy day'! – The Old Wives' Tale by Arnold Bennett