Sometimes saying why you changed your mind can help. In more detail than “his position seemed better than mine”. But sometimes it takes doing some action that is in line with the new idea in order for other people to think you may be serious.
Another thing that may help is to wait some time before telling the person. “Later that day” makes it seem like a quick turnaround. Waiting until the next day to say something like “I’ve had some time to think about it, and I think you were right about X” might make more sense to the other person and lessen the incredulity.
Also, it depends on what your past history has been with this person, and what they have observed in your behaviour.
Sometimes saying why you changed your mind can help. In more detail than “his position seemed better than mine”. But sometimes it takes doing some action that is in line with the new idea in order for other people to think you may be serious.
Another thing that may help is to wait some time before telling the person. “Later that day” makes it seem like a quick turnaround. Waiting until the next day to say something like “I’ve had some time to think about it, and I think you were right about X” might make more sense to the other person and lessen the incredulity.
Also, it depends on what your past history has been with this person, and what they have observed in your behaviour.