It all depends on each individual student. Many science and math courses have a reputation of being difficult, but again that depends on each student's strengths and weaknesses. I wouldn't advise you to pick a career field based on level of difficulty. I would suggest you think about potential careers that interest you and then thoroughly research those careers. Find out exactly what the career entails, which schools have the program for that particular career, how much earning that degree will cost you, what the potential job market will be upon graduation, and what type of starting salary you can expect. It is wise to have as much information as possible in order to help you create your academic plan and feel good about it. It may very well be that your passion lies in a career field which requires you to graduate from a challenging program. If you are dedicated and willing to put in the work, it will pay off in the end.