To be two sides of the same coin

Example #1
Bob: I feel sad today. I don’t know why. Yesterday I was happy.
Tina: Well, sometimes we are happy and sometimes we are sad. Actually, you can’t have happiness without sadness, just like you can’t have day without night.
Bob: I think I understand. Happy and sad, like day and night, are two sides of the same coin.

Example # 2
Leo: I hate rain.
Roberta: But you love the flowers that grow after the rain, right?
Leo: Well, yes. I really love flowers. They are so beautiful.
Roberta: Remember, Leo, the rain and the flowers are just two sides of the same coin.
Leo: Wow, I guess you’re right. Thanks for the kind words, Roberta!

Definition: When two things seem to be different, but are part of the same thing: Yin-yang.

https://languagesystems.edu/