Your back is at it's most vunerable state first thing when you wake up. This is due to your discs being fully hydrated and at their highest pressure point, thus more open to injury. When we move our body and back, such as bending and twisting, a force is put through the discs in your spine. Your discs have an ability to withstand these forces up to a certain point, however this ability is decreased whilst fully hydrated. A continuation of poor posture and form during movements will create wear and tear on these discs, which will eventually lead to the discs being completely worn or acute injury such as a herniated disc.
My tip is to make sure you keep a neutral spine whilst getting out of bed, sitting at your breakfast table and getting changed. If you can manage this, then you'll be less susceptible to spinal injury and back pain!