I can't help you based on experience, but family, social life, leisure time, maintaining a healthy lifestyle, etc. sound like valid reasons. Of course, with goo

I can't help you based on experience, but family, social life, leisure time, maintaining a healthy lifestyle, etc. sound like valid reasons. Of course, with good time management, you can have all that and be productive. If your startup is split 50/50, then you should each be putting in the same amount of work. This is hard to measure in time because some people are a lot more productive than others, and hard to measure in output if you two are focusing on different problems (e.g. software development vs marketing). Also, no one likes to be constantly nagged at, it makes them feel as if they're being treated as a child. You could be pushing him away without knowing it. I suggest spending more time socializing, maybe go have fun with your cofounder, and keep your mind off the startup while you're socializing (unless the event is geared towards discussion about the startup). Also try working in the same location rather separately, or working together while at the same location. This could help motivate him.