Stop movement first – break second: Ever tried to hit a moving target with a punch? You quickly learn it's a lot a harder than hitting a stationary one. So too in grappling. breaking or strangling a moving opponent is usually significantly more difficult than one who has been immobilized. So take your time to first focus on IMMOBILIZATION and only when that has been satisfactorily achieved, switch to the task of breaking/strangling. There is a reason why some submission holds have a higher success rate than others – its most due to the ability of that hold to immobilize an opponent. The juji gatame arm bar being used here by Georges St-Pierre uses your legs to pin your opponent's head and shoulders and as such makes it quite easy to pin even very strong opponents. That's one of the main reasons why it is the most successful of all the arm locks in competition. So when it's time to okay the submission game – divide your task in two. Focus first on restricting your opponents movement. Only then go on to the subsequent task of finishing. You may not be able to do it every time, but when you can you will be impressed by the results.
