"you are vacationing" is correct because it's a continuing event. And we are talking about one (long) vacation that is currently in progress, continuing.
"I am coming" doesn't work. It's an event that happens, and then is over. Think of it in terms of an airplane "I am landing here regularly" - no - you land here frequently. Each time you land, it's over, and then you land again. You can say only that you "are landing" is during the actual event itself, and if it is "are landing regularly" that means that that one particular instance of landing is regular, rather than irregular. The only time you will hear "I am coming" is either as a promise of future attendance at an event, or during sexual climax.
"I am growing" might work as growing is a continuing project. It is so well understood that you don't grow something in an instant, however, that you can just as easily and correctly say, "I grow only the sorts of flowers that ...."
So, to state it simply, if the event is currently in progress, you can use the form
"I am kicking" myself for not having studied harder.
"I kick" that damned waste basket every time I come around that corner.
Both examples are in a present tense.
Student or Learner