Patience with toddler tantrums

Hi everyone. My son turned 3 on the 3rd and he instantly started having tantrums especially at bedtime. I am normally so calm and patient and we can talk it out and solve the issue as I do not believe in hitting my kids as retaliation for the way they are feeling. Tonight, it took be 3.5 hours to put him to bed. I was able to calm him a few times but then he started screaming at the top of his lungs and he hit me super hard in the face. I know this is most likely a result of him being very tired, however, I lost my cool and I yelled at him. I feel like the worst mom in the world and cannot sleep. After I yelled at him I took a minute to calm down and brought him in my bed and let him know I was sorry and I cuddled him to sleep. This mom guilt is debilitating. Does anyone have any words of advice or encouragement to make me not feel like th worst human being. I think I feel so bad because it was right before he was going to sleep