5. It will backfire
If you try to work during health issues, you most likely will not be producing your best work. So, while your intention may have been to improve your standing at work by foregoing paying attention to your health, you might begin to be seen as sloppy or apathetic instead due to the health struggles you are battling with. If it is mental health that is your struggle, you could find yourself lashing out at coworkers or appearing unstable in the office if you do not seek help immediately. If you don't want to take off of work because you need the money, consider how much money you will lose if you develop a serious health concern and have to pay for hospitalization and treatments that could have been avoided if they were addressed immediately.
So, take those days you need. It will help your work in the end.