Would you recommend investing in a 403B account when the market is doing so poorly?

Yes. Remember the adage "buy low, sell high?" The market is certainly low, and through dollar cost averaging every month you stand to do quite well once the market recovers. This assumes that your time horizon until retirement is more than just a couple of years. Get in the habit of investing every month, set up a diversified portfolio of stock and bond funds, rebalance your account maybe once a year, and the account is certain to do well over the long term.