Could just as much be down to the resistance of the system (including mouthpiece, obviously) - some players like a lot of resistance coming back at them, some really, really don't! There's an odd phenomenon that some sop players sometimes encounter which sounds alien until experienced... where you get to the end of a phrase and can't help but breathe OUT before you can breathe IN (and the breath in is often then quite uncomfortable) - tight-ish mouthpieces on tight-ish instruments can build the the point where a healthy breath is more than you need and you're exhausting the O2 in your lungs before you've blown the whole breath out down the instrument. In such cases, a more open mouthpiece will usually help (not necessarily a deeper cup, though not unlikely, but bigger throat bore and/or bigger backbore), though with less resistance comes an increased need for proper breath support to prevent pitch rocketing sharp in the upper register. Psychology is definitely part of it - there are plenty of vicious cycles you can get yourself into quite easily... Among them, missing the wood for the trees - thinking about small factors and forgetting to pay attention to the big factors (for example, thinking about things like mouthpiece placement and forgetting to take decent breaths and keep the air supported.... leading to intonation getting worse and you tiring out quicker, and getting more fixated on everything else except the breath support you really needed!). If you think it might be mouthpieces I have a few of varying styles (deep/shallow, tight/open, etc) and I'm not far away if you want to try them.