OK, if you get the admittedly much tougher follow-up question as to why you were let go (and the truth isn't exactly pretty), your best bet is to be honest (the job-seeking world is small, after all). But it doesn't have to be a deal-breaker. Share how you've grown and how you approach your job and life now as a result. If you can position the learning experience as an advantage for this next job, even better.