You have to demonstrate that you are unable to perform Substantial Gainful Activity because of your severe medical condition and that that inability to perform SGA will last or has lasted 12 months or longer. It is hard to be found disabled while you are working. It is possible, but not easy since you are showing that you are able to work by doing so. You have to show that you are unable to do more work than you are actually performing and that you cannot earn over $1050 (changes every year) even if you are able to drag yourself to work now. You can show that your employer gives you breaks that other employees don't get; you can show that your performance is not worth the amount of money you are being paid and your employer is keeping you because of a a personal commitment to you or because you are family or that you get extra help or paid or unpaid assistants. SSA can reduce the earnings by Impairment Related Work Expenses if you have a significant amount of out of pocket expenses that you pay for that allow you to keep the job that a non-disabled person would not have to pay.

The link you were given is for work incentives that apply to a person AFTER they have been entitled and AFTER they have been disabled for 12 months. Returning to SGA less than 12 months after onset can reopen the award to a denial.