My husband is upset because I didn’t initiate our sex schedule

Dear Roe

My husband and I are married for nearly 20 years but we still argue about sex issues. My husband’s drive is much higher than mine. We agreed on having sex twice a week, and that I would initiate it – but two weeks passed and I couldn’t initiate it (tired, busy, wasn’t up for it). I tried in the third week but he is very upset and is not in a good mood. I don’t understand how he can be so upset. We have gone through the same situation multiple times in past years but I don’t understand the behaviour that a person can get so upset and can’t move on from this.