If you don’t like the username then it is very likely that you won’t like the product either. If you do like the product but the username, is not your style then be prepared for a tough decision. You see, we can all change depending on the circumstances but the first thing you can do is read up on the user experience and the features they like best.
Now comes the point where you are forced to evaluate the current user experience and then, go with an option that you like.
If the username is not your style you may need to consider getting a new profile picture and possibly a new account name for your new website. You can still use the old profile picture and link the brand if you like along with some of this new information. You will have the option to change your username to reflect your new image and new info but may not want to do that while your partner is still on the site.