My co-founder Andy remains one of my best friends, a board member, and close confidant. We had our ups and downs, but we’ve managed to stay in close touch and I’m excited to be an investor in the startup he’s now CEO of. We eventually split because he wanted to be the CEO of his own business and didn’t just want to be the CTO or tech guy… and I can’t at all blame him.
There’s an Inc Magazine article about how we went to marriage counseling together. We had a few moments where we fought and he suggested we get coaching or joint counseling to work out how to best argue with each other and it was actually quite helpful. Also helped get me on the cover of Inc magazine 
We also established clear ownership areas and swim lanes. I worry about X, he worries about Y, and we’d have collaboration and information sharing about Z. We also worked in isolation in different parts of the office or home so that we didn’t see each other all day long.