I think bad tempers are too often excused away as a foible of our personality, when in fact it can be really hurtful to other people and inexcusable, and says there are some root issues that need dealing with.
Very recently I exploded at a dear friend and said a couple of crazy unwarranted things, and later it tore me apart. The fact that I hadn't slept properly for several nights and was running on the edge may have kind of contributed but wasn't an excuse. It made me realise the degree to which unresolved crap inside me was building up.
We do all have off days, but I've realised lately how often in my life I have been running on a short fuse. It's ugly, and something I'm determined to deal with.