I remember losing Lily (my first female) over 4 years ago, just like it was yesterday. I was totally unprepared for how hard it would hit me. I didn't realise quite how attached to her I was until she was gone. She died in my lap and it was the most awful experience. I totally understand how you are feeling right now - that sense of emptiness and how much of your day you suddenly have spare because there is no misting and feeding to do. Lily's viv was empty for a week before I got my second female and that was the longest week ever. They are part of the family and I know I couldn't be without mine.
I have since gone on to lose Tommy and Amy and each time it hits just as hard, even if you half expect it. What it teaches you is to watch them so carefully and take note of what exactly is 'normal' for them so that you can pick up instantly if something isn't quite right. Even with that knowledge, you still can't save them. Both my girls were at the vets at the first sign of trouble and yet that still wasn' enough. They hide illness so well and that is really hard to deal with.
Lastly, anyone who says 'It's just a lizard' should be given a hefty slap - unless you have had the privilege of sharing your home with a chameleon and fully understand the bond you can have with them in such a short time, you cannot begin to understand the huge sense of loss at losing one. They are much more than 'just a lizard' and it makes me so sad to hear them talked about in that way.
The fact that you feel so bad now, means that you are a good and caring owner and that can only be a good thing for your new litle green friend! Please post pics when s/he arrives so we can share in your joy too!