Head banging

Tonight I was trying to let my little one go five minutes if crying before I went in to sooth because he’s up a lot at night and it’s no good to anyone. Well, he sat himself up and started rocking and purposely banging his head against the crib slats. I actually am aware that toddlers sometimes bang their heads when frustrated since they don’t have words yet, and a google search says this is common in some babies at night. But it made me feel awful and the rules of my sleep training went out the window. I mean, even if it just is something he does and it’s no big deal, I don’t think I could ever just watch that behavior and wait it out. I feel like I’m never going to sleep. By the way, all the websites say babies outgrow it.... by age 5! That’s so unhelpful. Ugh. Anyone else? He also pulls his hair from time to time.