All major spiritual practices physically begin with the breath for a very good reason - it is establishing a default path of least resistance for energy flow, establishing an energy potential that will absorb the energies that you work with while cultivating. Any master worth his salt will prescribe lots of meditation for this reason, some wont continue to teach you if you arent obeying that rule.
Energies raised, especially in the head, need to be grounded back down, the potentials brought back down, at the end of a session. You'll notice some ignorants say meditation invites spirits, or the devil, lol. No, not grounding the energies worked with in the head will serve to burn one's nerves up and make one a bit loopy. YMAA recommends scalp massage after meditation.
Quiet the nerves; the olfactory nerve inputs a 40 cycles/sec resonance into your midbrain. How to stop that from happening? Train the breath properly, then you quiet your mind from the neural level all the way on up.
Once the mind is quiet, then things can happen.