Most people that I have smoked with that wasn't prepared for the effects of Cannabis ended up having a panic attack. IMO there is no way to prepare because everyone responds differently and until you finally do experience being high enough times it usually is a bit strange because your body is introduced to something it has never encountered before. And don't worry, the rushing thoughts and worrying is a normal thing is just something that happens until your mind gets used to THC. After you are very used to marijuana even if you take a break for a loooong time and come back, being high still won't bother you. Might be a little too strong but you'll know how to handle it. It's just something that comes with smoking marijuana for so long lol. So just take your time and don't get discouraged. If it's your option to continue to use weed then do so and in due time you will be glad you did .