It's more of a niggle than outright bitterness 
Colleague and I are both doing an online module through work for a graded certificate. We had coursework due to be submitted yesterday. I've submitted something I'm really not too happy with but accept that it's my own fault for not getting started on it sooner. I emailed colleague today and he mentioned that he got another 5 days to do his as he requested an extension. He pretended he's been sick to the course leader so he could get extra time. It was awarded instantly without any evidence.
Why am I so annoyed at him? Is it jealousy? Annoyance at myself?
If only I'd known it was so easy to get extra time, I would have done it myself! Is this why I'm so annoyed?
Why would you feel annoyed if you were me? Feel like I need an impartial opinion here.