It depends. If you edit elements, the personalizations remain intact. If you delete them, it might impact your personalizations.
Personalizations are like an additional layer of information that is sent to your website visitors. The difference between the personalized web page and the original one is described by a delta (or a diff). Every time you adjust content through Unless, a new delta is created.
When someone visits your website, Unless sends out the delta and replaces the original content. So technically, a personalization is just a group of content changes on top of your original page. It is not a separate, new page.
In general, changing the original page will not "break" your personalizations. In fact, updating texts or images will have no effect. However, if you delete elements your personalizations might not apply.
Let's say the headline of your original page is "Unique Bouquets for Mother's Day". Next, you create an Unless personalization and change the headline. So far, everything will work smoothly.
However, your colleague decides to delete the headline of your original page entirely.
Now, the following happens: Since your colleague removed the headline, the delta has nowhere to "dock", meaning the personalization isn't applied. To fix this, you can either re-add the “docking” element or go into debug mode and connect the personalization to a new element.