Invite the person who disagrees with you into the planning. Critics make excellent co-pilots.

Opposition from outside a plan is a problem and the same opposition inside it is a resource. Someone who thinks you are wrong is already hunting for the flaws, and with them in the room that work improves the plan instead of undermining it. They also tend to support what they helped build. Leaving them out keeps the objection alive without giving you any benefit from it.

Bring your clearest critic into the next planning conversation and give them a real part. Ask where it breaks before anyone praises it. Take at least one of their changes so it is obvious you meant the invitation.