What is "grace", (not the religious kind)?

If you're taking about movement, it refers to movements that are smooth and continuous, making complicated results look effortless to achieve.

If you're taking about interpersonal relationships, it means one party not taking offence at the actions of the other, or not scroring the wrongdoings of the other. This is closely related to one of the religious uses of the word.

If you're talking about a timekeeping, a "grace period" is a short time after deadline where good-faith entries will not be counted as late.

If you're talking about competition, a "grace period" is a portion of the contestant's performance that will not be scored.

https://en.wiktionary.org/wiki/grace

Broadly speaking I would describe it as acting in ways that accept and work with things as they are, rather than resisting the truth of the situation.