Join the club. I had a very similar experience with my step 1 scores and ultimately scored almost a full standard deviation below my practice exam scores. I was quite disappointed, thought the world was ending, etc. etc. Now, I finished my year as chief resident a couple of weeks ago and I had a very productive residency experience that I really enjoyed. I'm writing this from Japan on a trip with my wife, exploring the Japanese countryside, and incredibly excited to start at an academic position that fits exactly what I want in a job in about 3 weeks. I can't wait to get my career launched and am excited for what the future holds.
This disappointment seems so great because at this stage in your training, step 1 seems like the most important thing you have ever done or will do. In reality, it's only one milestone in your training, and its importance will quickly fade. It's easy for me to say that, but just know that this is not the end all be all. You will still be able to do something that you love, you will still have a great life, and you will still have a fulfilling career. Step 1 is done so there's nothing to be done about it. Time to focus on continuing to work toward your goal, which, based on what others have said, seems entirely feasible.