In very simple terms, your subconscious cannot distinguish between a real event and an imagined event.
So if you want to powerfully build up your belief system, feed stories of success to your subconscious mind. Your belief will begin to skyrocket because your mind sees 'evidence' of that success all around.

I prided myself on my multi-tasking abilities and the ease with which I could switch from coding to marking to 3D design while holding simultaneous conversations in Messenger (text) and Skype (voice). I was Successful!