Northern Lights can be a strong strain if grown correctly.
Sounds like you had a big anxiety attack. It happens to all of us at sometime. I had a bad one with a new strain about a year ago. The important thing is to always remember that cannabis is harmless, it will not and can not kill you or hurt you in any way. You just smoked a very good strain that you were probably weren't ready for the effects.
I would just take it easy with some of the more powerful strains till you are more acclimated to there effects.