a trick you may try is really studying the animal. look for definition in the animals face, or maybe the body and see if you can see the scoring lines without the aid of binoculars.

another trick is get behind the stake, way behind the stake. if a target appears to be set long, but you cannot tell, get back and look at it.

or, judge to an object behind the target. a 40 yard tree may catch your eye, and tell you the target is actually 36 yards.....

as for your problem of second guessing, it never really goes away, just spend time shooting your bow, and judging yardage. it becomes easier, but the second guess and getting tricked on yardage never goes away.

you said in your post you are a longtime fita shooter, so you have the shooting down pat im sure, spend a lot of time just judging yardage. take a rangefinder out and judge things at the park, or on a walk, or where you hunt. take it to practice range and keep a log of how you judge. after 30 targets see if you tend to judge short or long. there will be a tendency and keeping a log will help you find your weakness...

just remember, if you dont put the yardage on your sight, the arrow will never get to the target.....i hate to take yardage out if i get scared of my guess.