You can use the cards, just don't carry a balance. If you don't use a card ever, it's likely going to get cancelled.
The easy thing you can do is set recurring bills only to a credit card and then set that card to auto pay the entire balance each month. Something like Netflix or even your electricity bill.
Put the bill on the card, and if you don't have the willpower to shove the card in the back of a drawer and never use it, cut it up. The card doesn't go inactive, you don't rack up debt or interest, and you can maintain a high credit to debt ratio.