We’d recommend following the plans as closely as possible, however, it’s not essential that you sleep exactly in line with the sleep cycle in your plan or even stay in bed for the exact period.  The sleep cycles you choose (and can tailor to fit your personal schedule) are there to assist and encourage your sleep based on common, modern day sleep patterns and circadian rhythms.  Everyone is different and we’d recommend you to try to listen and adhere to the natural patterns of your body which can even vary day to day depending on how (particularly physically) active you are during the day.  So if you wake up before the full sleep cycle is complete and do not drift back to sleep we’d suggest you to wake up and start your day even if it’s very early.  When aiming to get back into natural sleep patterns it can sometimes help to shorten your time in bed.  In other words it’s not always beneficial to be in bed if you’re not sleeping.  At first you may feel additional tiredness during the day, but this tiredness may also start to bring on  sleepiness at the end of the day.   In addition, actual time needed for sleep differs for everyone so it’s best not to assume that the often quoted 7-8 hours is necessarily right for you.