Today, most of us are taking better care of our health. We’re more active, get more Vitamin D, and stress a little less. As for our finances, sometimes these feel-good vibes — including summer vacations — cause us to amp up our spending. If your wallet is starting to sweat (like ours), then Ashley Feinstein Gerstley, author of The 30-Day Money Cleanse, is here to whip our finances back into shape. In Mailbag, is it smarter to pay additional money toward the principal on a home mortgage or to invest that money in an index fund?