I've been doing HIIT for a while. Always very intense and I end up demolished and definitely not feeling better afterwards, just really tired. I asked my train

I've been doing HIIT for a while. Always very intense and I end up demolished and definitely not feeling better afterwards, just really tired. I asked my trainer if it ever gets any easier, in his words, "No, you just get stronger". Feeling subjectively better after a workout session might be in the same line as "happens to some people".