With a new type of training, higher intensity than in the past, and inconsistent training leading into there was several new things for your body to handle. You have a smaller buffer zone with inconsistent training leading into your intro. Good to hear the symptoms were gone the next day.

The buffer zone will increase as you get into better shape and are consistently training.
You will have more experience using all the different energy systems.

Yes, in feels good to push yourself. Intensity was higher for where your current level is.
Dialing back the intensity some as you start classes is a good idea.
As get use to working out, working out on back to back to back days(if you’ll be doing this) and the type of training your buffer zone will increase. Talk with your coaches about increasing intensity levels.

Getting quality sleep, healthy nutrition, hydration, and stress are factors which impact what you body is able to withstand. When one of these are not where it needs to be dialing back some for the day may be needed.
Life happens to everyone. An awareness when something needs to be dialed back is key. Be proactive.