Bring your whole self
So far this month, I've had to convey this message to two founders. You may need to hear this, too. There was a time when I definitely did.
They want to work with you because they trust your judgment. If you work with them against your better judgment, you're not just playing yourself but also playing them. They have a lot of respect for you. Have enough respect for them to tell them the truth and work through the consequences.
If they're making a go/no go decision and looking to you as the company leader for advice on whether they've done enough diligence, they're asking for your expertise, not just your praise.
If they're an engineer who thinks there's a market opportunity for a piece of technology they'd love to build and ask you to do it with them, they're asking for your judgment, not just your compliance.
Yes, they'd love for you to agree with them. They want to move forward on this with you. But they want you to agree with them because you're convinced, not because you feel social pressure.
I had to learn this one the hard way. It almost cost me a twenty-year relationship and burned me out. We're still repairing parts of it. I just wanted him to be happy, but it's a hard act to keep up.
The problem is that you can only keep following a path you don't believe in for so long. The dissonance will build, and you'll eventually have to tell them why you're acting funny. You might even admit you've had reservations for a long time. Suddenly, the floor falls out from under them.
They'll feel betrayed. They misunderstood their situation. They thought they were working with someone they deeply respected on a problem you both mutually believed was hard but worth a shot. But they've been alone, out on a limb this whole time.
You're their protection against feeling foolish, and instead, you'll become the cause of their embarrassment. You think you're doing them a favor. You see how good they feel working with you, and you're happy to see them happy. But they won't feel that way anymore.
Don't coddle them; they're an adult. Just tell them the truth. They can take it. Tell them how you feel. Even if they're sad now, they'll know they can trust you. They asked you because of who you are. So, be your whole self in the situation; be the person they know you to be.
After all, If they wanted anything less of you, you wouldn't want to work with them in the first place, would you?