When is it okay to think? It seems like you're supposed to do the dishes, drive your car, etc. and always be mindful of the present moment, but when is it okay to think about something like a work project or a hobby or something besides the moment? Even when you're meditating you're supposed to not be thinking... It feels like the only time you're allowed to think about things is when you're sitting alone in a dark room.
"In the original Mindfulness Sutra, The Buddha described what he called the Four Foundations of Mindfulness. These teachings remind us to be aware of our bodies; aware of our feelings and emotions; aware of our thoughts; and aware of events, as they occur, moment by moment." Lama Surya Das, Awakening the Buddha From Within, pg 301-302. (Italics are mine.)

Obviously, mindfulness does not mean that we should not think, rather that we do not dwell on the past, and stay in the present moment. If the present moment means that you need to think about future plans, that is acceptable. Just realize that those future plans are not set in stone, are subject to change, and will be in the present moment when they are implemented in the future.

As for meditation, it sounds like you are describing Samatha, or Calm Abiding Meditation. This does indeed call for training the mind to not have as many conceptual thoughts during the meditation. If one arises, we are aware, and dismiss the thought by returning to the object of focus, such as mindful breathing. The following link may be of assistance to you. 

Contemplation and meditation and thinking