What are your typical daily habits, how do you live your life?

Do you exercise, do you meditate, do you drink enough water, do you eat well?

or..

Do you smoke cigarettes? Have a poor diet? Lack of exercise? Lack of mental and spiritual development?

Troubling sensations are often manifestations of how you treat yourself.

although, to quote a very useful passage of The Psychedelic Experience

"Here is a list of commonly reported physical sensations: 1. Bodily pressure, which the Tibetans call earth-sinking-into-water; 2. Clammy coldness, followed by feverish heat, which the Tibetans call water-sinking-into-fire; 3. Body disintegrating or blown to atoms, called fire-sinking-into-air; 4. Pressure on head and ears, which Americans call rocket-launching-into-space; 5. Tingling in extremities; 6. Feelings of body melting or flowing as if wax; 7. Nausea; 8. Trembling or shaking, beginning in pelvic regions and spreading up torso. These physical reactions should be recognized as signs heralding transcendence. Avoid treating them as symptoms of illness, accept them, merge with them, enjoy them."