I have found that if I look at the needle I don't sew straight. I keep my eye sort of fixed on the point where the fabric enters the foot. Even a little before that and have the needle in my peripheral vision. If you look at the needle it's too late to nudge the fabric a bit. It has helped me especially with SID. And, also, slow down. And I still sew some crooked seams but not as many. I think I learned this from a Holice video.