The proper taper differs by person. This one is too fast unless your brain really isn't that used to it. Psychiatrists usually tell you to take half as much every other day for a couple of weeks, then reduce it again, but again, it really depends on how it goes.
I was thinking that if I was to taper, I'd do it like this:
Tonight and Tuesday = 1 1/2 tablets
Wednesday and Thursday = 1 tablet
Friday through Monday = 1/2 tablet
Tuesday through Friday 1/4 tablet
Benzos are a bad remedy for insomnia, as they interfere with the brain's ability to learn how to adapt to stress and interfere with REM sleep, and of course are addictive with quite a withdrawal kick. Although you only used it for a short time, people are different in how they respond to quitting -- it should be done gradually even after short term use if that use was continuous as opposed to as-needed occasional use. Don't know anything about Sonata, but all sleeping pills can be habit forming. If you're looking for a cure, therapy to see if there's an underlying cause that can be dealt with, natural remedies if they work since they're not addictive such as melatonin or herbs or homeopathy -- much gentler than drugs, though nothing is consequence-free, Keep in mind that doctors in general are ignorant of the drugs they prescribe and completely oblivious to their more unpalatable consequences -- they're taught by pharmaceutical companies, and it;s bad for business to admit you might harm someone and bad for the emotional state required to go on as well. Very complicated stuff.