So last night i was in bed doing affermations in my head that i was going to have a lucid dream. After a while i felt my self start to drift and i think fell asleep for a time or atleast lost presence of mind, but it felt like only a fraction of a second and when i regained conciousness, it felt like i was tilted back and into my bed on a small angle and it felt like someone was sitting on my chest and it was difficult to breath, i tried to remain calm and go with it and i was able to for a while, but it was taking a lot of concious effort to keep taking in air, eventually i could hear my lungs taking the air in very loud in my ears, and i could hear how i was struggling to draw breath and i panicked and snapped into conciousness and sat in bed. Are there any suggestions on how i can keep myself calm, or what measures i can take to prepare for this in the future?