When expressing your preference to walk instead of taking a taxi with someone, it's essential to be respectful and considerate of their feelings. Here's a polite way to communicate your decision:
"Thank you for offering to take a taxi together. I really appreciate your kindness. However, I prefer walking today as I find it enjoyable and it's a nice opportunity to get some fresh air. I hope you understand, and I look forward to catching up with you later."
By using this approach, you acknowledge their offer and show gratitude while respectfully expressing your preference for walking. It's always best to be honest and kind when communicating your decisions to others.