I’m an advocate of putting your career first.
But I’m also an advocate of loyalty, honesty, compassion, dedication, fairness, and gratitude.
And your decision goes against every single one of those things.
She did nothing to you, but you chose to throw away 5 years of her commitment and effort like it was nothing.
You’re using your career as an excuse because you think that sounds better than saying you fell out of love with her. People fall out of love, it happens. But at least you should have been honest with her about it or try to work on your relationship.
You couldn’t have been so busy that you had to neglect your woman. She should have been your support and your pillar. So yeah, you should feel guilty.
But maybe not so guilty, because she deserves to be with someone better.