When you have to stop when a quilting line has ended, you need to secure the stitching by backspacing a couple tiny stitches. You then cut your thread before moving to the next stitching area. It helps to cut both top & bottom threads (at the fabric) as you go as it saves looking for tails to cut later on. When starting again, secure the stitching with a backspace or two before continuing on. I cut those tails after I have gone a couple inches. It's like cleaning up as you go.