Around here , losing one's temper commonly means to get angry. More broadly, 'losing it' means losing one's composure, a word that is somewhat synonymous with temper but, at least as far as common usage goes, composure is not particularly suggestive of anger.
Thank you so much for your help. Ah, yes, of course! I think I understand. People sometimes lose control when they are very excited. It could be because of great joy, or it could be because of terrible fear.....! In these cases, I can use 'lose it.'