Is it a big deal to focus on differences between the two? Perhaps it is, when it comes to natural commitment. This is how it works:
Passion refers to what you really like to do. It could be painting, speaking, driving, swimming, writing, or even just being a couch potato! This is “you”, and your passion is truly yours. This is what you love to do no matter what. This is where you find solace and take refuge in difficult times. This is what makes you happy and lets you enjoy for being who you are.
On the other hand, profession refers to what you do for a living. It could be painting, speaking, driving, swimming, writing, or anything else that lets you earn a living. This is serious business. You have to abide by rules and procedure to stick to norms and standards. You must strive for continuous development and updates in your field to perform better. Sometimes, you might just have to cling to it, even if you do not like it.
Fortunate are those whose passion turns out to be their profession. Fortunate are those whose profession, after a while, becomes their passion. Natural flow of commitment would be expected in both the cases. However, if your passion and profession widely mismatches, you could just be an average Joe trying hard to make a living. Let me know if you find any exception.