Q: Where do thoughts come from?
A: Right now if you wish you can think of your favourite actor. This thought is coming from conscious mind. You can bring this thought whenever you wish. However, a thought that just pops in without you consciously desiring it comes from causal body/karana sharira (unconscious mind). What thought will pop in from causal body depends on the activities of conscious/subconscious mind. Your conscious/subconscious mind is actually a tuner. When it is in resonance at certain thought frequency, it attracts that type of thoughts from the causal body. On a side note, since it is about tuning, if you identify with misery, you may attract chain of thoughts close to misery and the opposite is also true. Now, you can choose what type of thoughts you would like to harbour and which types of thoughts you would like to kick out the moment they pop-up in your mind.