Why am I feeling this way?

Hey y'all, im going to keep it short and simple. A year ago big changes happened, I lost my career that was a big part of me. My ex boyfriend who I was with for 4 years left me for the tenth time, but instead of begging him to stay this time I told him to stay gone forever. Decided a big change meant I needed some help. Went to therapy and tried to unpack a lot of hurt and pain from this situation. Unexpectedly 7 months after a bunch of healing and working out, I fell in love with my bestfriend who I've known for years it was sudden and unexpected. I didn't want to be in another relationship for awhile since I felt that was best, but things happen and fast forward 6 months and I couldn't be happier. All these insecurities and jealousy that I thought were just apart of my identity are no longer, I feel secure and safe. I also, got into another medical field and will make decent money. Yet despite all this comeback I find myself still aching sometimes from the pain especially around the one year mark that was this past week. Sadness over my ex and how he discarded me and my career that I once loved and had so much hope for. So I guess my question is, how can I be happy and sad at the same time?

Why am I feeling this way?
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