If Grammarly or another writing assistant changes your tone, treat its suggestions as optional edits, not automatic improvements. Accept grammar fixes that remove real errors, but be careful with suggestions that change wording, confidence, warmth, urgency, or formality.
Tone matters because it carries relationship context. A message to a teammate, a customer, a professor, or a client may need to sound natural, direct, polite, or careful. A polished rewrite can accidentally make the message sound colder or less authentic.