How can you explain being born under a zodiac sign that doesn't match you at all?

Are you sure it really doesn't match you, or is it just that you don't identify with the generic description you read everywhere?

The thing is, astrology works a lot through confirmation bias. You read that Sagittarians are adventurous and sociable, and if you are too you're like "yeah that's totally me". But if you're introverted, you'll forget that trait and focus on another one that fits better. The descriptions are broad on purpose, so there's always something that can match. Plus your sun sign is just one part of your chart - there's your rising sign, your moon, all your other placements. If you think your sun sign describes you badly, maybe it's because it's not the one that dominates in your thing.

But honestly, the real reason is that you're never just one box. You're complex, you change depending on the context, and reducing someone to "you were born in July so you're this" just doesn't work for everyone. Some people find it fascinating and really see themselves in it, others think it's all nonsense. It's normal that it doesn't fit you - it doesn't mean anything's wrong.