How not to feel guilty when you think you did the right thing?

Yesterday, my older son (just 2 years old) did not want to take his medicine and he did not! His attitude was a mixture of "I do not want to do what you ask me to" and "I am really tired and sick, let me go to sleep". I told him I was upset with him and put him to sleep without the normal sleeping-time ritual.

I feel sooooo bad and guilty. What is the right thing to do? The worse is that it was in the evening(no time for reconciliation).

It is not easy to be authoritative and the one who gives calins...