Dreaming about cardboard means temporary prevention and avoidance. Although mistakes are prevented initially, it will creep up again. Tasks may have been avoided, they will be reassigned to you in the future. Instead you should take this as a sign to get your act together in the waking hours, so you can tackle the core issues to make yourself whole again.
Cardboard is often seen as a cheap and worthless material, and may symbolize your own feelings of worthlessness or low self-esteem in your waking life. Overall, the presence of cardboard in a dream may suggest that you are feeling unimportant or undervalued in some aspect of your life. It may be a good idea to reflect on what is causing these feelings and work on building your self-worth and confidence.