You're preaching to the choir, lol. There are days where I'm convinced I haven't lost a single pound and the scale must be broken because I still clearly weigh 300+ lbs. It those mental barriers that make losing weight so darn difficult. To get out of the funk I try to focus on the changes I can see (like my wrists are a lot smaller than they used to be, and for the first time since high school I can wrap my thumb and index fingers around my wrists and they touch). Also, I just started taking progress pictures of myself and it's been really helpful to compare the before shot to the current pictures.
Just know that we all have those days where we slip into the dark scary place, but it will get better. We all slip up now and then, it's ok because nobody's perfect. You've lost over 50lbs and that is incredible!!!! Be proud of all you have accomplished & stay strong!