Dear He,
I am writing to inform you of my decision to resign from my position with your company. This was not an easy decision for me to make, but it is necessary for personal reasons.
I have enjoyed my time with your company and I am grateful for the opportunity to have worked here. I have gained valuable skills and experience during my time with you, and I will always remember the good times we had.
I wish your company all the best in the future and I hope to keep in touch with you all.
Sincerely,
Eswar