The easiest way to discredit someone is to point out something he/she is not.
If you’re a designer, don’t let people judge you on your coding skills. If you’re a marketer, don’t let people judge you on your design skills. It’s great if you have those skills but, what you bring to the table has value on its own.
You have skills, strengths and weaknesses. Unfortunately, you can’t be good at everything all the time. There’s a time for everything; eventually your skill set comes in handy.
But, if you find yourself consistently short on skills and strengths where you work, ask yourself this question, do people value what I bring to the table? Your skills are just as valid as other peoples’, maybe you’re just not sitting at the right table…