You have a close relationship with your boss, so you will announce your intention to leave the company in a private, one-on-one conversation. However, you also recognize the need to write a formal letter of resignation, which you will hand to your boss during this meeting. This letter is addressed to your boss, but as formal business correspondence that will become part of your personnel file, it should not be a "personal" letter. Making up whatever details you need, write a brief letter of resignation.