Here is examples of Quit letters.

It is with great sorrow that I am hereby tendering my resignation to you.
Although there is much to say, I believe the reasons leading to this decision
are known by you, and I will therefore leave them unsaid at this time.

I appreciate having had the opportunity of being a member of this company
for so many years and offer my best wishes for your continued success.

Sincerely,

Your name

PS:
Your custom message

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Quit your job online today at http://iQuit.com! It's FREE!

Unfortunately I must resign my position in the company effective
immediately. Please do not ask me why I have decided to move
on as I am not willing to discuss it.

Thanks so much for nothing.

Sincerely,

Your name

PS:
Your custom message

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Quit your job online today at http://iQuit.com! It's FREE!

I would like to resign my position with your company immediately.

Sincerely,

Your name

PS:
Your custom message

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Quit your job online today at http://iQuit.com! It's FREE!

I have finally come to the conclusion that this going no where
dead end job can no longer be part of my life. It is incredible
to me that you and your company have made it this far and I
will be very surprised if you are able to stay in business
being such a Boss Name.

I have never been so dissatisfied with such a lame company!

Sincerely,

Your name

PS:
Your custom message

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Quit your job online today at http://iQuit.com! It's FREE!