An English word (adj or verb) to describe your feeling when you did not do something you were expected to do

I am looking for an English word (adj or verb) to describe your feeling when you did not do something you were expected to do. For example:

My friend's uncle has just passed away but I didn't say anything to him when I first heard the news because I was focusing on something else. Now looking back, I feel very bad about it. I should have said something. I feel ______________.

The word is pretty close to 'regret' but it's not 'regret'.

Solution 1:

Remorse fits the bill.

From MW:

a gnawing distress arising from a sense of guilt for past wrongs : self-reproach

Oops - per Hank's suggestion: remorseful.

Solution 2:

The classic feeling of shame is perfect for what you are describing.

shame (noun): a painful feeling of humiliation or distress caused by the consciousness of wrong or foolish behavior. ‘he felt a pang of shame at telling Alice a lie’ (Oxford)

Also, mortified works here.

mortification (noun): great embarrassment and shame. (Oxford)

e.g. 'When I thought back on how I handled the situation I was mortified. And even today, I have a lingering feeling of shame.

Solution 3:

I would say that you are feeling regretful that you didn't do something you should have done.

re·gret·ful (adj): feeling or showing regret (Oxford)

You also might be feeling disappointed in yourself and your actions.

dis·ap·point·ed (adj): sad or displeased because someone or something has failed to fulfill one's hopes or expectations (Oxford)

Guilt-ridden or guilty would also work, since you are feeling that you should have done something, but didn't.

guilt-rid·den (adj): filled with feelings of guilt (Oxford)
guilt·y (adj): culpable of or responsible for a specified wrongdoing (Oxford)

You may be ashamed that you did not do something that was expected of you.

a·shamed (adj): embarrassed or guilty because of one's actions, characteristics, or associations (Oxford)

A simple feeling sorry might also work in this context.

sor·ry (adj): feeling regret or penitence (Oxford)

Anguish might also work if you are really upset about your action, but that option would lean toward a more extreme feeling.

an·guish(v): be extremely distressed about something (Oxford)