Is it worth it?

You have your moments and are trying to push boundaries.  Recently, you make promises of 'last time' or 'last one' but then will ask for 'one more'.  We gave in to you initially but realised that the 'one more' became more and more often.  So recently, we became strict with the 'last one'.  This caused you to throw a tantrum and cry, and then end up in the 'naughty corner', which delayed bed time a lot more than just giving in to you.  Is it worth all this hassle and screaming?  Hopefully these thoughts run through all parents' minds?