How to write a letter to get your money back that you lend

To Unthankful colleague :

Dear John,

I am frankly uncomfortable to ask, but I know it must have slipped your mind. When I lend you $2000 last month, you said that you would return it after the week-end. Could you please send your person with it today?

I look forward to receive the payment at the earliest.

As ever,
(your name)