Couriosity
This is probably the most important. As long as you manage to stay courious what a training will be like, how it will feel, what will happen, joy is not far away.
Health
Equally important for joy in training is being healthy. Nothing being more frustrating than an injury or a body which just does not run smoothly.
Being not in shape is much less frustrating than being sick or injured
Mindfulness
Being in-the-moment, feeling ones body, not thinking about what else to do,…
Contentment
Many people loose joy in training because they think too much about a time when their shape was much better. Or because others are making faster progress than them. We try to invite us to pick us up where we are. And enjoy whats possible there. And progress from there.