I don't sew over needles - I've broken needles by forgetting I had a straight-stitch foot on and switching to zigzag and a bit of broken needle HAS flown up and clicked against my eyeglasses. Thank goodness I'm blind without them, or I could be blind now! LOL
I just hold my seams if they're about a foot or shorter, that's usually enough. If I'm putting together longer pieces I use Clover clips and just take them off as they're about to hit the foot. They're easy to remove one-handed, just press down and slide to the side and they let go.
For anything that's really critical and absolutely must stay put all the way under the needle, Elmer's is my "grabber" of choice.