Why is my toilet always running, and how can I fix it?

Your toilet may be running due to a faulty flapper valve or a problem with the fill valve. To fix it, you can try adjusting the chain on the flapper valve or replacing the flapper if it is worn out. You can also adjust the fill valve to ensure it is working properly. If these steps do not solve the issue, it may be best to contact a plumber for further assistance.