how difficult is to be a pharmacist?

I believe you need to be good in Chemistry

http://www.coreynahman.com/pharmacy_Information.html

There are many things you may wish to consider when exploring the possibility of becoming a pharmacist. Typically, one should consider both the steps involved in the process of becoming a pharmacist as well as the career options available to Pharmacists. Even more importantly, you must consider the responsibilities and qualifications of a Pharmacist relative to your own abilities.

http://www.pharmacy.purdue.edu/students/prospective/