as i said, nictoine is a non-factor. as for caffeine, i quit multiple times. once the headaches are gone, which takes a week or two, followed by another week, or few, of feeling lethargic, it is back to normal(ie. give it a month altogether). so it's not too bad. it might be also easier to wean off slowly by decreasing caffeine consumption over longer period than quitting cold turkey to avoid the negative effects altogether.