A lot has to do with how often you shoot.The people that have the most problems are those that shoot infrequently.A friend of mine used to shoot quite well until he moved to a different city that does not have a local range.He went from shooting a lot to shooting only to sight in his gun before the season.He now has a terrible flinch that he never had before.Another friend has lost interest in practising during the off season.He too has developed a bad flinch that cost him an animal this past fall.It seems that those that shoot often but not too many shots at an outing are able to get used to recoil and overcome any tendency to flinch.
In any case I would not resort to a muzzle brake as the great increase in noise can quickly damage hearing and can cause flinches as well.