Leaving a sport after training for so long is hard no matter what. I will say that the biggest challenge that surprised me was getting used to is not being on a team -- I played an individual sport all my life and yet this was still the most difficult (emotionally, mentally) as you lose that bond and support system that only sports/teammates/coaches can give you.

Stay active on your own terms (which is a positive, but watch out for body dysmorphia), explore new hobbies because you're going to have so much more free time, and look for a community that supports and pushes you! Whether it's friends or a group for a hobby/activity. Ex-college athletes often love beer leagues for kickball or softball, or pick up something radically different. I run and lift ~5x/week, I have friends who coach kids in their sports as a side hustle, we've done fun things we've always wanted to try but never had time to, etc.

One thing I will emphasize though is that there is definitely a period of identity crisis and changes in body/self image. Don't get too down and remind yourself that you are entering a new, different chapter! Your body is still strong and capable! Enjoy and congratulations.