Think of all the things you do with your keys before you actually insert them in the door locks:
* You throw them in your bag
* You leave them on every table and desk you can find throughout the day
* You forget them at your lawyer's office and you are lucky if you remember to go and get them again (did you get the right ones?)
* You use them as a tool for your scratch ticket
* You try to insert them in the wrong security door locks
* You let your children play with them
Let us remind you that your keys were made for an entirely different reason. If you don't start taking care of them, you will soon be locked out and wonder how did you get yourself in this situation! There are certain rules when it comes to keys (although people hardly follow them, but then again that's why they are often faced with key trouble that inevitably leads to house lockouts). Do you want to belong to this group of people or make a new start and hardly have such issues? The choice is yours.
If you choose to follow the rules, start by checking your keys. Are they bent or damaged in any way? If you find the smallest problem with them or the tiniest scratch, it's best to get a key replacement. It's also wise to get some spares and keep them in safe places. Don't put them all together and avoid putting the spare in the key chain where you keep the original (it will be pointless). It's also important to take care of them throughout the day. Stop throwing them on tables or letting pets and kids play with them. Apart from running the risk of losing them, they might also get damaged.
One of the reasons for keys breaking is that they are rusty. Erosion eats up metal from within and makes it very vulnerable to breakage. One day, you will simply put the key in the lock and when you will try to turn it, it will break. Keys don't break easily when they are in good condition, but don't press your luck. If it is not inserted in the lock or doesn't turn, there is a reason for it. Don't put force. It's best to extract it and try again gently. Later on, you can check the key or even proceed with lock repairs to see why you had a hard time using it. For now, be nice to them!