The management technique of the day is capitulation, or the art of giving up.
In today's age of choice, it is difficult to force someone to do something they disagree with. I run into this problem all the time at my company, where about 25% of the employees are former founders, co-founders, or CEOs of various businesses. We all like to believe that we're always right.
But the fact is that the need for focus does require startup teams to make tough decisions about what to do (and what not to do).
One of the most powerful techniques you can employ to get your way is capitulation, or simply letting other people do what they want, rather than trying to convince them to your point of view.
This technique has to be used carefully, because you don't want to develop a reputation as a doormat, but can be extremely effective when dealing with the strong-willed and opinionated.
Put simply, sometimes the cost of letting someone else figure out that they're wrong is less than the cost of trying to argue them out of their preferred course of action.
Let's say that you and your partner are considering a project which will take about 4 hours to complete but cost very little cash. You think it's a bad idea; your partner thinks it's a stroke of genius.
You could try to persuade him to your point of view, but you might very well spend more than 4 hours arguing, and even if you won out in the end, he would always feel resentful and think in the back of his head, "Things would be better if only we had done it my way." Regret is a powerful and corrosive force in human psychology; we are far more likely to regret what we didn't do than what we did.
If you capitulate instead (and do so gracefully--a grudging capitulation ruins the technique), one of two things will happen. Either your partner will discover that you're right and he's wrong, which will help persuade him to listen to you the next time you have a disagreement, or you'll discover that you were actually the one who was wrong, in which case your business will be better off.
Either way, you save time, energy, and goodwill, and probably get additional benefits in the bargain.
Capitulation lets you make your point in the only way that really works: Letting the other person discover the truth for themself.