Tips for becoming frugal again after living a little too lavishly?

I used to live frugally by necessity. Then I started making more and lifestyle creep got the best of me. I developed spendy habits that have been hard to kick. Food/delivery, clothes, “little treats” for my mental health. I don’t like how I’m living and I want to go back to being frugal, but when I restrict my spending I just feel sad and like it’s taking the joy out of life. Any wisdom to share?

Edit: thank you so much for all the responses. I have received practical advice, creative ideas, and perspective shifts that inspired me. Blown away at the kindness and resourcefulness of this sub. Thank you! I’ll be implementing many of your suggestions.