The smoke should be directed into the upper teeth. If the smoke is directed to the roof of the mouth, you've got the pipe stuck way to far into your mouth. As I clench, the tip of the the bit, any bit, vary rarely passes my teeth. Don't know if I painted a decent picture. Hope so. The pipe rests so the smoke either goes up into the upper teeth (P-Lip) or is directed back along the teeth (fishtail), usually not across the tongue. I'm not doing a "wine" tasting nor, a "blend" tasting. I'm casually smoking as I go about my business, getting nicotine and enough taste to enjoy the tobacco.
If you are smoking while working, as I do, forget you've got the pipe clenched and/or get into better shape so you aren't "panting" from the exertion. Or, work slower. Wee sips, normal breathing works for me. I generally breath through my nose or, around the bit, not, through the pipe. I can, sometimes unintentionally "over do it". But, never to the point where I am sucking heavily on the pipe, heavily enough to burn tongue or mouth. I never have my lips "sealed" around the bit.