If you do not set the rules rights then running a business with your soul mate could be a recipe for disaster. Well not everyone gets an opportunity to work with someone you trust, and this could be the ultimate strength. The biggest asset is that you know the strengths and weakness of your spouse. The rewards could be big if you handle the situation with maturity. But if things turn out to be worst it could end your marriage or relationship. Even couples who have a good rapport otherwise have arguments over a business. If you demarcate the boundaries and stick to strategies, a business relationship could work wonders between soul mates. Agree to a business plan that suits both your passions. Do not work together just because it is a passion of your spouse. Unless you have good understanding of the business never venture into it.
Always keep separate workspaces to avoid arguments and walk into each other often. This could give some privacy and peace to work out your ideas. Despite work taking first priority, taking time out to hang around with each other could give some relief. Briefing each other on the development on the work front could help running a business. Planning activities could be fun and interactive. Also, this can help to charge the batteries. The best advice would be to change roles quickly while in office and home. Being opinionated could lead to problems. The right way to get out of the problem is to listen. Finally, learn to forgive for the mistake instead of aggravating the situation with heated arguments.