I'm just about to start session 3 (challenging negative thoughts) having found the first two sessions really helpful - but am wondering how best to challenge negative thoughts that could be true? For example, I have a fear of flying and it's possible (though highly unlikely) that I could die in a plane crash. It's the possibility of this that makes me anxious, even though it's very remote. I still fly, but get nervous for months beforehand. How best should I challenge these thoughts?