I am grateful to be employed by you before a few months ago, working with you and other colleagues in your computer company. It is the most one of(one of the most) wonderful memories in my life.

　　But I find, in recently, the job is not fit for me, and I have decided to quit this job. I would like to give you my apology for resigning the work. There are some main reasons accounting for this as follows. For one thing, the level of my health is declined by the jobs pressure.

　　I would like to travel by myself in order to relax mental and physical. In addition, my previous major can not match for the features of the work. For another, I believe I am not interested in computer science by working months. Please accept my sincere apology for any inconvenience my leaving caused. I look forward to hearing from you.