There is a widespread custom for the bride and groom not to see each other during the week before their wedding (or at least for a few days or, failing that, on the day of the wedding itself.) This is quite a recent custom, and the source is unclear.
The Rema (Rabbi Moses Isserles) writes in the 16th century that bride and groom should only see each other in the company of chaperones in the run-up to their wedding.
There are, though, reasons why the custom seems like a good idea. Firstly, absence makes the heart grow fonder; separation can heighten the couple’s love when they are reunited on their wedding day. Secondly, the days before a wedding can be a pretty stressful and unromantic time, full of niggling issues around last-minute table plan changes, flower arrangements, clashing outfits, etc which could cause wear and tear on the couple’s relationship if they get too involved.