Not remembering dreams is quite common. Norepinephrine is associated with long term memory formation, but acetylcholine is associated with your short term memor

Not remembering dreams is quite common. Norepinephrine is associated with long term memory formation, but acetylcholine is associated with your short term memory (e.g. remembering some random digits). When you dream acetylcholine is high. That is why dreams "slip" away from your mind so quickly when you wake, it's the same reason that a random series of digits is hard to keep in your working memory. I believe this support the interpretation I put forward. Typically our anxious behaviours are reinforced in our dreams (which should highlight their presence if we are paying attention to them). If these were added to our long term memory, they would reinforce the behaviours they are trying to highlight, in order to eventually have the waking you eliminate. It would be counter to this goal if reinforcing experiences were added to long term memory, adding them to short term memory means they don't leave a reinforcing imprint. It's not so easy to remember dreams for this reason