Spice definitely isn't going to burn up your brain or anything. I usually get intense, but pleasant feelings in the head any time I smoke spice. They usually increase with dose. Maybe you were ready for the mental breakthrough but the body-load was something you hadn't expected and so fought against.
I've had friends who I introduced to spice and they expected a wacky trip but weren't ready for the bodyload, some even gagged. On their second try they expected the heavy body load(more of a lightness IMO) along with the visual trip and didn't have any problems letting go.
Next time be sure to remind yourself that this chemical is already in your body and cannot do any harm to it. If you handled the visuals of the breakthrough becoming use to the body-load should become easier with practice then just "let-go" and let the trip run its course.
In the province of the mind what one believes to be true, either is true or becomes true within certain limits. These limits are to be found experimentally and experientially. When so found these limits turn out to be further beliefs to be transcended. In the province of the mind there are no limits. However, in the province of the body there are definite limits not to be transcended.-J.C. Lilly
The Spice must flow
Zat was Zen and dis is Dao.