You can help a friend de-stress in many ways that will let them know how much you care about them. Simply motivating them is a great place to start.
You can send them a care package with some goodies that will make their day. Going to a yoga class with them or getting them a spa day or a massage is a great way to improve their mood. Spending fun times with them, making them laugh, and just being there to listen will be sure to touch them deeply.