The Cause of Self Doubt and Limiting Beliefs

In the natural unfolding of life, there are several impulses to do things. A lot of times those impulses come from a sense of separation which could be defined as desire or awareness. These impulses often stopped by self doubt fear or limiting beliefs. So I got three questions that are interrelated all of them in this context. How can one discern between an impulse that comes from the sense of separation versus awareness? The second one is what is the cause of self doubt limiting beliefs which basically creates suffering in humanity because you are going against life. And third, if you could give a practical example of how to overcome self doubt and limiting beliefs in order to manifest what is essential to us which is consciousness.