So maybe you almost fell asleep and something worke you up, or you woke up in the middle of a dream. You have two choices, and each have their own benefit.
1) Work backwards through the dream remembering and writing down each detail. This helps with memory and will help you remember your current and future dreams.
2) Continue the dream similar to how you would force start the dream of your choice. For example, if you are driving down a road and you wake up, you can continue driving down the road. DO NOT OPEN YOUR EYES. Opening your eyes will bring in your other senses and cement you into consciousness. If you instead just continue with your imagination you can slip back into your dream state.
Although you should realize that if you become successful with this technique you will not remember the dream when you wake.
Pff. I honestly would rather prefer to remember my dreams than have a mild sleep dissorder that makes it hard to wake up…