Challenging careers can be challenging.

for me the most important element about choose a career is hobby. You can do your job greatest only when you love it.

Hello my dear, I think every new career is a challenge, and what's important is our attitude toward solving such challenges ! Life is great and we should enjoy it, and if we find something challenging that we like we should try to do it even if it may seam hard at first. Hobbies are great, and volunteering is a good way to experience challenging fields before going to work, to learn if one can enjoy the aforementioned fields.