Please treat this as a formal letter of my resignation from my position as (your designation) of (employer’s name). The effective date of my resignation will be on (last day of your employment).
I have enjoyed my stay with the company as much as I have loved doing my job. I was able to acquire new skills and knowledge that I know will help me in whatever endeavor that I take in the future. I feel, however, that it is best for me to withdraw from the company because (state your reason for resigning).
If there is any way that I can help with the turn over of my responsibilities, please do inform me and I will be more than willing to help. I hope that this 30-day notice is enough for the company to find a replacement for me. It was never in my intentions to inconvenience you or the company due to my resignation.
It was a pleasure working with you and I wish you all the good fortunes and success in the future.