I must be unlucky because most strains of marijuana give me terrible panic attacks. The sativa heavy or hybrid strains do it every time, and with indica its a dice roll depending on how long the smoke is in my lungs. I inhale and then immediately exhale (the smoke is in my lungs for less than a second). One hit and bam! I'm as high as I need to be (and it feels great). Any higher makes me feel like I'm having a heart attack.
Contrast this to some of my friends who can smoke bowl after bowl of super buds and still write good assembly language.
It's probably better for my health but I do wish I could smoke more, feel the good effects, and not get crazy paranoid.