Busy might mean: lots of calls, lots of emails, lots of fires to put out, lots of switching from task to task, lots of ideas floating through your mind, lots of talking about acting on things, etc. In short it means you had a lot going on but it does not necessarily mean you had a lot getting done.
If you feel "productive", however it may be more about making tough decisions, completing something that had been hovering, finally acting instead of talking, and yes, generally, completing more work.
Busy might mean opening more things, productive might mean closing more things. Busy might mean more YESes, productive might mean more NOs. Busy might mean more plans, productive might mean less plans but more prioritization. Busy might mean more more, productive might actually mean less.
Lastly, despite the fact that world might not be cooperating with you at all times, it's important to remember that most of your day is really about the choices you make and control.....
Is being and feeling productive really a choice and do you control all the things that go into feeling productive? If you say yes, you will probably be right and if you say no, you will probably be right also. So how will you describe your day tomorrow?