Since joining Dreamstime and being bitten by the bug, one of the biggest problems I have come across is a very simple one... time.
I don't know what the proportion of amateurs to professionals is here on DT, but I suspect that the majority of people selling images are doing so as a hobby, or at least a part-time addition to their regular job.
This obviously raises the problem of time. Shooting images, processing RAW files, retouching, and for that matter creating illustrations, all take a significant amount of time. Which is sometimes hard to find when you are holding down a full time job and doing all the things which occupy our day to day lives.
One solution is to let the house get dirty, buy takeaway meals and paper plates, and hire a gardener! Or it may be more sensible to think about changing your priorities. Maybe you could allocate one or two nights a week to your image processing. Or instead of going to the pub in your lunch hour, you could sit in a cafe with a coffee and a notepad, and come up with image ideas.
Make every Wednesday night your 'Shooting night', or do your housework on Saturday morning, and some shooting on Saturday afternoon. Allocating time in your schedule for these activities may increase your chances of actually doing them, in the same way as if you have an appointment at your dentist.
Hopefully these ideas may help you to take a step in the direction of turning an enjoyable hobby into a fulfilling and successful career.