I have a love for hand piecing as well as hand quilting. In the beginning I had the same problem as you and spent a lot of time untangling knots. As you get better you realize that you are making those knots because you keep flipping your thread in circles. Try using thread only as long as your forearm that is form wrist to elbow. You will find as you improve the length of thread you use will grow longer. Also keep your thread moving left to right or right to left as the case may be so you are not putting those knots in it. You will find your stitches and enjoyment improving as you gain confidence in your work.