If you are adamant about something in a dream, it can be a sign that you do not express your opinions very forcefully in waking life.
You may have difficulty making up your mind about things, or you may feel that you cannot openly express your opinion.
Your dream is telling you that you need to be more decisive, or that you need to let others know how you feel.
Dreaming that you are adamant about something can be a way for you to relieve a need to express yourself when you feel that you cannot do so in waking life.
Your dream could be telling you that it is better to be honest about your feelings and beliefs and deal with the consequences of that honesty than to hide your beliefs and feelings.