Robert E. Lee was woefully outnumbered, he had nowhere near the resources or supply lines, and he still held his army together. The Civil War was by no means a sure victory for the Union for the first two and a half years perhaps. The Union suffered several grievous defeats in the first few years and if not for Gettysburg? If not for losing Stonewall Jackson? Who knows?
But even after it was a lost cause they kept fighting and that's something I respect. Many of those men weren't slave owners and it makes me sad that history likely view them through that lens. Many of them were dirt poor fighting for their homes and their families and for states' rights.