I sometimes think of playing a melodic line as skipping across stepping stones. If you're playing within your capabilities, any slight inaccuracy in the hop from one stone to another can be adjusted on the fly and little harm done.
But when you push it a bit, the inaccuracies can build up, and tension rises in your embouchure, the root of your tongue, your shoulders and eventually, with apologies for the most appalling of mixed metaphors, it all collapses into a hideous train wreck.
I guess all of us can feel this starting to happen, and start looking for a sustained note where we can readjust and regain our balance. But if that's not available, do you have any reliable techniques to disperse the tension and regain control?