I've posted several times about the value of routine.  Having a pattern for your regular activities can help you develop a rhythm and make sure that essential tasks get done.

But your routine should never become dominant.  If the choice is between your rouine and someone's need or your routine and an amazing option, the routine should be the loser.

Strive to keep a healthy balance between planning and flexibility.  If they are in balance, they actually help each other.  Having the basics well in hand will give you the freedom to take advantag of opportunities as they arise.