We had a sponsor daughter at USNA who was gung-ho Marines from Day One. She spent an exchange semester at USMA and fell in love with some of the career fields there. After careful thought and discussions with both Marine and Navy mentors, she persevered with the cross-commission process, attending both Marine Leatherneck and Army summer training blocks in her firstie summer. She found a better fit for herself, the stars aligned on both sides, and she was successful.
Look at it like a relationship you've been in for a few years. An attraction develops for someone else. It's either transient or enough to make you go through the steps to break up with current steady and pursue the new relationship!