I don't regret helping that individual but my experience does help me realize that a good face may have poison behind it. I never expected anything back but this experience helped me learn not everyone you help will help you when you need it the most. I wish him the best in his career and his life.
My advice to all of you is, choose your friends wisely during medical school. Always help anyone who needs it but have your guard up. Don't blame them if they can't help you, may be it's out of their hands. But it's better to be straight forward about it. You will know who will take that extra effort to help you even if they were not successful.
Remember success is leased everyday; you have to work everyday in order to old on to it. It's going to be your friends and co-workers who will help you hold on to success. If you turn your back on them when they need your help, then you have a higher chance of loosing your success.