[Your Name, & Address here]
[Recipient Name & address here]
This is just a short note expressing my concerns about you.
I am aware that you are presently working on the [Project name]. I know this is a time consuming project and, thus, you are a bit stressed out.
However, I want to tell you that when you will successfully accomplish this new task, you will feel a great sense of achievement. You will feel proud of yourself.
I have great confidence on you that you will successfully complete this project.
Wish you all the best for this important assignment. I think of you and look forward to meet you once you are done with this project.