A bruise from training fades in a week. A habit built in training lasts years.

The part of hard training that hurts is also the part that disappears soonest. What stays is quieter: being somebody who turns up, who finishes the set, who does the warm-up when nobody is checking. That gets installed by repetition and then follows you into jobs and classes with nothing to do with sport. The soreness is the price, not the product.

Pick the habit you would want still running in five years and give it a fixed slot this week. Watch the attendance rather than the aches. If something hurts in a way that is not ordinary soreness, get it looked at rather than proving a point.