Beginners fill every pixel. Professionals leave room to breathe. Whitespace (negative space) separates good design from great design.
Whitespace Creates Grouping
Elements close together are perceived as related. Increase space between unrelated groups. This is the Gestalt principle of proximity.
More Space = More Premium
Compare luxury brand websites to discount retailers. The difference is often whitespace. Generous padding signals quality and confidence.
When in doubt, add more padding. Then add a little more.