When a relationship is still pretty new, you typically want to do your best to put your best foot forward and make a good first impression. You're careful what you do or say, not because you're trying to hide parts of yourself from your partner or be dishonest, but because you don't want to do or say anything that's embarrassing, particularly in front of someone that you still might not be the *most* comfortable with. After awhile, though, even the embarrassing things have to happen. If you do these embarrassing things in front of your partner, they're ride or die. Almost assuredly.
Embarrassing yourself in front of anyone can be, well, embarrassing and sometimes even a bit stressful as well, especially if you're somewhat shy. It can take a long time even being comfortable doing some things in front of your closest friends, roommates, and even members of your family. And while your partner often sees you in all manner of undress and at your best and worst, there are still some things that you might be a bit self-conscious about doing in front of them until you feel more certain that they're going to be around for awhile and you're sure you can be the most comfortable about them. Once you start feeling OK letting them see even things by which you're embarrassed, you'll have a much better idea of whether or not the two of you are meant to be.