I can assure you, it is possible (Score 1)

Don't try and compete with the younger, full-time students. Learn the information for the information's sake. If you own your own business, your GPA doesn't matter as much as a newbie just graduating. If you will sacrifice a few GPA points, you will learn the same amount of critical information, you just don't spend a lot of time learning the last 5% of what the professor likes/doesn't like for answers. You will find no difference between a 3.9 and a 3.0 for your purpose.