A natural focus is your own breath, which is always with you. If you simply keep feeling the breath as it comes in and as it goes out, the mind gets quieter and more peaceful.
The only trouble is, something will always take your attention away - maybe a noise …..or a pain in the knee…..but often your own mind is the problem, it is so full of useless stuff! Like a monkey jumping here and there, it is so hard to control.
To become the master of your mind, you need some lessons, enough time and a good place to learn how to practice.
With enough practice, meditation helps to replace bad thoughts and feelings with happy ones. (See more under Why Meditate?)