At it's most basic level, meditation is supposed to reduce stress, to calm us, make us happy. Sometimes this doesn't happen. Why?
Sometimes it's the wrong technique for us. Although my path has been yoga, I had a friend who was always a bit disturbed after doing meditation. It was an energy pathway one, combined with chanting Om out loud. Preceded by bhastrika (a very fiery breath), bandhas (energy locks) & nadi shodan (alternate nostril breathing). He went on a 10 day Vipassana retreat, loved it....& calmed down. I hoped he would continue with the buddhist technique as he seemed so at peace whilst doing it.
And I have noticed, & experienced, that very strong energy meditations can be hard to maintain, especially if one has not been taught how to calm down first. You would think that nadi shodan would do it, but if you were doing it with big breath retentions, long counts & even bandhas.....perhaps not.
What is missing is learning how to calm the breath, thereby calming the body, mind, emotions, prana (life-force), & most importantly, calming the awareness so that we are seated in a Higher Consciousness. Or, if we are not quite at that yet, then so that our conscious everyday awareness has calmed down.
Ujjayi on it's own will not do this. We need to slow down the breathing, whether ujjayi is used or not. We need to stop "powering up" the energy, because, ironically, this just makes us agitated & creates internal energy blockages. And we need to slip into the internal realms quickly. There are pratyahara (sensory withdrawal) practices but I find they make me restless. One is being like a tree.....really? I find that silly.
If postures have been done prior to meditation, using slow, relaxed breathing will take us automatically into meditation. We will not be able to resist. So, if you are teaching, or doing a practice on your own, you can most definitely do strong &/or dynamic poses...but...& this is important, there should be a slowing down as you go into seated forward bends & twists, & inversions. They don't have to be hard poses, but even if they are just reclining stretches, that will do the trick. relaxing, calming & cooling poses. All three combined.
Throughout the class..or even just at the slowing down period at the end, breathe this way: as you exhale, gently pull the navel back towards the spine. Pause briefly, for a fraction of a second. Relax the abdomen as you slowly inhale, then another brief pause. Keep going like this. ......instant calm, instant happiness. It will lead you right into the inner realms. You can continue breathing like this as you meditate, but you most likely will automatically do similar breathing without having to deliberately breathe like this. Meditation will become much easier.