On a small scale maybe try printing the cards and give it to friends. Get their feedback and iterate your idea from there.
You could also setup a Instagram/Facebook/Twitter Account where you post one of your idea on a regular basis and gain some audience. If you’ve gained enough audience you can then print the cards, bundle them, and sell them online . I say bundle because It won’t be worth it (because of shipping and hassle of paying) if they just buy one card at a time. Print it in a book and they just tear the card when they need it. If you are familiar with the Starbucks planner, I am thinking similar to that. Group them by occasion or mood so they can easily find it.