To dream of curtains represents concealment or secrecy. Alternatively, it may reflect repression of ideas or information.
To dream of shutting the curtains represents you attempt to conceal something or keep a secret. Your repression of ideas or information. You are concealing some personal matter or something about yourself.
To dream that you are opening the curtains, represents your readiness to reveal something hidden about yourself. Revealing the truth or a secret. No longer feeling the need to repress ideas or information.