Small cities are warm and big cities are too deep.

This is a very subjective view. Different people may have different understandings and feelings about "small cities are warm-hearted" and "big cities are too deep". Here are some possible explanations:

1. Social environment: Big cities are very different from small cities. Small cities may be more familiar and intimate, and people have closer relations and a higher degree of mutual understanding and support. This may give people a warmer feeling of living in a small city.

2. Competitive pressure: The competitive pressure in big cities is greater, including employment, socialization and culture. In order to stand out from the fierce competition, some people may adopt some routines or strategies to improve their competitiveness, which may give people a feeling that the routines in big cities are too deep.

3. Lifestyle: The lifestyles of big cities and small cities are also very different. Small cities may be more traditional and comfortable, and family and friends get together more, which may give people a warmer feeling of living in small cities. The lifestyle in big cities may be faster and more modern, and people's lifestyles may be more diversified and personalized, which may give people a feeling that the routines in big cities are too deep.

In short, this subjective feeling varies from person to person, and everyone has different experiences and feelings, and may have different opinions.