Not to worry — we all miss sessions at some point for many different reasons. Don’t be discouraged :)
The poses / sequences do become slightly more difficult as you progress through the program. If you have to take a few weeks off from training, then we recommend that you pick up from where you left off.
If you are finding it a bit of a struggle, you're more than welcome to go back to a place where you feel more comfortable and continue on from there :)