It's for this very reason that I'd suggest synaptic, rather than aptitude, for beginners. There are times when aptitude will have a strange chain reaction wherein it finds some packages that it deems no longer required by any other program, and ends up listing half your installed programs as useless junk to be thrown away. Like a cleaning person gone mad. Even after closing and reopening aptitude, in such a situation, it will still insanely want to throw away half your OS, falsely claiming everything to be broken (it no longer lists anything as broken after the user presses cancel pending action, however).That seems like a pretty dubious assertion. Synaptic's interface is "pretty", but seems quite clunky compared to aptitude's. As far as I know, it's also missing one of aptitude's most useful (even/especially for beginners) features, automatic handling of packages dragged in by dependencies.
A newbie might not know that pressing using the option to cancel pending actions would be the best to take in such a circumstance.
Mark