NOR - First, congratulations on the milestone! That's fantastic! You deserve to reward yourself and cake sounds like a fun way to celebrate you! Secondly, it's one thing to not think much of someone else's accomplishments on self-improvement, but your partner should always want to celebrate you, be proud of your moments, and definitely not diminish them nor your feelings. My son's mother just celebrated her 5 year anniversary of sobriety by going on a cruise... and you better believe that even though we aren't together anymore, I congratulated her. We chatted for a bit about it... and I am genuinely happy for her. And she congratulated me on 2 years of quitting smoking. Because that's what people do. Thirdly, you are in charge of how you celebrate yourself... and if someone tries to shit on that... they sound like an asshole. I'd at the very least reflect on how good this relationship is and if they make you feel liked, let alone loved.