"Reward good behaviour, not the bad ones" If he's doing that because he didn't get his way, make sure na you don't give in just because he's hurting himself. Ginawa ko before sa lo ko, hindi ko sya pinapansin, I try not to have any reaction-- no worry, sadness, fear, etc. I don't want him to get the idea that he'll get attention/ whatever it is that he wanted just because he's hurting himself. My lo stopped doing it soon after.