Jobs and covering letters

My boss' job has just come up and although I am not sure that I really want it, I feel that I must apply for it, for my own self-esteem and who knows, perhaps something might come from it! But it is just such a pain having to write this Covering letter. As a Tefl teacher, this is one of the things I ask my students to do, but it is not until you have to do it yourself, that you realise that it is not so easy. I suppose it does give you a moment to sit back and to think: what would I do in this position? Well, it has done for me.