Yogi: How can I be aware of my thoughts as they happen?

Sayadaw: Right now when we are trying to practice, when we have to intentionally think, it is hard to be mindful because we also have to intend to be mindful.

It’s hard for the mind to do consciously when there are two intentions at the same time. But when you have been intentionally mindful for a long time, when the mind has some understanding of the nature of the awareness, the nature of thinking, the nature of knowing the object, then you can try to think of something and you’ll know that there is thinking, not because you’re trying to be aware, but because the awareness has become familiar with what thinking is. 

So you just need to practice to be mindful continuously.