Are there ways you can decrease your stress that are also eco-friendly?

I'd say Gardening is one. Planting trees, flowers or veggies creates more clean oxygen and soaks up carbon dioxide, and messing with soil is very soothing.

Walking and running is a simple activity that you don't have to spend money on or drive anywhere to do. Walking right out your door and strolling around the block is good for your health, helps you handle stress, and doesn't add carbon to the air.

Meditating and yoga - same thing, if you do them at home, or tack on a class while you are already out driving around anyway.

What else?