I've been living without a credit card for two years now, from choice. I buy everything by debt card or cash, and if I haven't enough money to buy something, I simply wait till I've got paid or do without. And thus my debts are falling very fast. I hope to become debt-free within a couple of years, barring my mortgage.
So many people spend so much time worrying about their credit scores, and there is a ton of articles out there giving advice about how to repair your credit score and advising you to do this or that to keep the lenders sweet. And the whole goal is so that lenders can lend you more money. We're all like trained hamsters running diligently along the wheel going nowhere. Yes, the fact that many employers are running credit checks before they employ is a concern which means that the score is important, but there is no reason to go overboard about it.
If you already have a mortgage, you already have a credit record. No need to borrow more to build a record. Therefore stop using those cards and start paying the debt down.
If you don't have a mortgage, things are a little trickier - you do need a good credit record to ensure that you can get a mortgage if you want to. But don't go overboard. Get a card, use it a few times, pay it off and then put it away somewhere. Don't borrow. The more you borrow the poorer you get. It's as simple as that.