It will take quite a long time before you find your calm, serene mind in your practice. Many sensations come, many thoughts or images arise, but they are just waves of your own mind. Nothing comes from outside your mind. Usually we think of our mind as receiving impressions and experiences from outside, but that is not true understanding of the mind. The true understanding is that mind includes everything; when you think something comes from outside it means only that something appears in your mind. Nothing outside yourself can cause any trouble. You yourself make the waves in your mind. If you leave your mind as it is, it will become calm. This mind is called big mind.
Zen Mind, Beginner's Mind Suzuki Roshi