Practice, relax and breath.
It does take time to get it right, practice. Try to relax when quilting, don't try to do it after having a disagreement with hubby (ask me how I know). Breath!! believe it or not I had to remind myself to breath, which in turn helps you to relax.
Is your work surface flat? Meaning machine and table at same level.
Is your machine height good? Elbows bent at (approx.) 90*
Look where your going!! You already know where you are!! Like driving a car, you look out further than your bumper ( I hope)
good luck