It's a very unfortunate circumstance to have this happen so persistently, and I do know who you're talking about, but I would think of it in two ways: 1) If you haven't created an enemy, you're not big enough to be called a success (hint: you are!), and 2) ignore them if they simply persist - that's the only way to make them go away.

Your persistence will pay off in the long run, and your strength will overcome.