If you relayed these sentiments to your co-founder would he understand or take offense? If your co-founder is level-headed maybe the right approach would be to say, "Look, this product is on the fast track to nowhere and it isn't doing any of us any good. Honestly, it's taking a toll on my health and it's putting a strain on our relationship. You're like family to me and I don't want that to change. I've thought about this long and hard and the way I see it, there are only two options left: we both agree to shelf this product or one of us should buy out the other. What do you want to do?"
