Eventually when you have been machine quilting for a long stretch of time you will begin to make mistakes. Mistakes that you are going to want to pick out. With out a good pair of tweezers you will be swearing and become very frustrated quickly. With out these you are never going to be able to pick out stitches that went wrong. I like tweezers that have a very sharp point and firm grip.
When I pick out stitches I use a seam ripper to cut the stitches on the back side of my quilt, then I turn it over to the front side and go about pulling and picking out the bad stitches. You want to work yourself back to a point where things where still smooth. You want to have enough thread so that you can tie off your threads and bury them. Be very careful with this process of using the seam ripper and pulling and picking out stitches because it is very easy to slip and rip your fabric. Then you really will be frustrated and angry.
My best advice to you is when you begin to go wrong with your quilting, STOP, don’t think it will get better if you just keep going. It won’t. Stop and pick out as few stitches as possible and stop quilting for the day. Take a break and come back tomorrow. Usually when you begin to make mistakes it’s because you are tired and you need to get away from your work for awhile and do something else.