Am I the only one..

id have to say it is very natural for a demon or something to leave bad energies

I can relate to these things.
I often feel the aura's of people, I can tell what kind of people they are quickly and if they're bad I usually can tell off the bat.
with the demon thing now, I've had (still have) some problems with that myself. spirits do try to attach themselves to a physical body sometimes, you should learn shielding, and banishing/warding off prehaps as well.