There are so many good reasons to bring your bag everywhere, here's a few:
1. rely less on natural gas and petroleum (plastic bags are made from petroleum)
2. create less trash
3. practice the most important of the 3 R's (reduce, reuse, recycle) which is REDUCE.
When picking your shopping bags, be sure that it's one that you like and won't forget to put in your car or bike everyday.
Here is a link to my line of reusable shopping and produce bags, that is if you like my style!