About the only thing that helps with my DS is to stop and say "do you want a cuddle?". Usually he says yes & "DS sad". After a while he'll calm down & forget whatever he was having a tanty about. It is also easier to talk once he's calm rather than when he's crying as he just doesn't hear anything when he's in that place. It can be hard when DD is also wanting/needing me or I'm in the middle of cooking dinner but I try to do this when I can. I think for him, it is a cry for attention. We have been doing this for a few months now & sometimes he asks for a cuddle without prompting. I don't think there is a simple long-term deterrent. Persistence & consistency is the key. Even then, there are still daily meltdowns over the littlest thing! It helps to have a process to work through in that situation though.