I agree with everyone who says you shouldn't be so hard on yourself. Didn't you fall when you first learned to walk? Didn't you fall off the bike when you first learned? Of course; we all do and each person her has been a beginner at one point also.
I have a Bernina Aurora 430 and had a lot of trouble stitching in the ditch before buying the #10 foot that goes right down the middle. See if your machine has a foot like this available. If not, know what I do? I zigzag the seams I want, right OVER that ditch. Makes it look effortless. If you have a decorative stitch that is wide, why not use that?
Just relax and enjoy what you CAN do right now. It will get better, I promise. When I made my first quilt, I pieced it all and put a backing on it, then turned it inside out, ironed it and thought that was quilting. My sister-in-law who works for HandiQuilt said, "Uhhh, Nolee, you just sewed it now you have to QUILT it." I thought it was all done with the sewing. NOW how smart do you feel? A lot smarter than I was, that's for sure. LOL