What does a diplomat do when, after four years, he or she has made little to no progress in ending a war that has claimed the lives of at least 350,000 people and turned an entire nation into a mountain of rubble? For the U.N.’s Syria envoy, Staffan de Mistura, there is only one answer: resign your post and hope the next mediator has better luck.

De Mistura, of course, insists he isn’t departing the job of U.N. special envoy to the Syrian conflict because he’s a quitter or because he has lost patience. Indeed, he’s most certainly not a quitter; the Swedish-Italian diplomat has more than four decades of experience serving the U.N., often in some of the organization’s most difficult assignments. He hasn’t built up such a long career by throwing up his hands when a situation is hard or a few speed bumps block the road to progress. If de Mistura has learned anything after decades of navigating the world’s many conflicts — from Ethiopia in the 1980s, Bosnia in the 1990s, and Iraq and Afghanistan in the 2000s — it’s that patience and determination are vital requirements in the business of diplomacy.