Dear Miss Zhang,
I am writing to inform you about my decision to resign from my current position for personal reasons.
The primary reasons are as follows. First, after three months, I do feel that it is not easy for me to get used to the extra work and night shift. Second, the salary has proven to be much lower than you originally promised, and I have a large family to support. Last, what I have learned at university cannot meet the requirement of being a journalist.
Please accept my sincere apologies for any inconvenience my leaving may cause. I wish you and the company all the best. If I can be of any help during the transition, please do not hesitate to ask.