Yes of course.
So many times, I have cancelled my power down process after getting the required Steem needed for what I want to use it for.
It doesn't have an adverse effect on your Steem or Steem related activities.
It just cancels any other Steem that would have come from the power down.
So, it is very possible to cancel a power down request once you feel like stopping it.
Yep! And many Steem users do that! :)
Since it takes 13 weeks to fully get the amount powered down, a lot of people choose to power down their 'whole' SP and cancel it after a week or two to easily get the Steem they want.
Take for example an account with 1300SP:
If the owner of that account is in dire need of 100 liquid Steem, then what he could do is fully power down his SP (1300SP). That would give him 100 liquid Steem per week. After a week he could just cancel the power down.
Compare that to someone who chose to power down only 100SP. That would take him exactly 13 full weeks to completely get that amount or 7.69 liquid Steem per week.
It is not that hard. Simply click on the Steem you have powered up and click on the cancel power down.
It is really that simple.