Why shouldn't I read in bed?

There is nothing wrong with reading in bed. The issue, when you are trying to fix a sleep disorder, is that reading in bed is an association between the bedroom and doing something other than sleeping. We need to start helping the body understand that the bedroom is for sleep. Stop doing anything other than sleeping in your bedroom, do them elsewhere.

In the future, when you become a good sleeper again, or when you are feeling a lot better, reading in bed won’t be the end of the world. But right now, especially if you are doing the sleep scheduling of Session 2, you’re going to find that the whole point of it is to spend time in bed sleeping and only sleeping. This might be a fairly restricted time to start with so you don’t want to overcomplicate things.

You’re trying to build that association between sleep and the bedroom again.