To walk or to drive to the grocery store?

That is today's question.

I'm about 50-50 when it comes to this. If I'm going to Safeway, I tend to drive because they have an easy in-and-out garage, and since I'm usually buying a lot of stuff, I just can't carry it all on my own (especially if I get milk and orange juice). But if I'm going to Trader Joe's (which is probably closer to my place), I walk. It all kind of depends on what the weather is like (I do not walk in the rain, obvi), what I'm buying (I tend to just get produce or cheese at T.J.'s), and whether I'm already in the car or not (i.e. if I'm coming home from work).

So is it lazy to drive to the store? Should I just always walk, and make several little trips every week instead of one or two large trips? How do you handle your grocery shopping?