I love yoga. When the instructor gives you the option of doing an easier pose, do it if you need to. Don't manly-man eat that shit. No one cares, no one is watching you. Take the easier pose if you need. In time you'll kick that pose in the dick. Take it easy on your first night. Don't get self conscious. Again, no one gives a shit about you, no one but the instructor is watching you. So don't convince yourself that they are. It sounds weird, but a lot of people work themselves into showing off or holding poses they really can't, because they worry how they look to the people next to them. Hot or not, they aren't looking. They don't care. Take care of you. I have low arches on my feet, pretty much flat footed. I regularly felt pain on the underside of my feet when doing warrior poses and the like. Turns out it's just that yoga mats are shit if you have flat feet. If that applies to you, do back-work on the mat, but when you're standing, including sun salutations, do it on the hard floor next to the mat. If you must have something under your flat feet, use a towel. Ujai breath is metal as fuck. Focus on that shit. Seriously. Breathing, holding, crushing poses by holding them long with staining muscles, breathing through it... Focus on that breathing.  Enjoy. Also stay clear of fats, they have no body control and will often talk/wine through lessons. Luckily snce I've done yoga for years I haven't seen a fat in forever, certainly not at a level higher than intro.