I can’t stop my mind from wandering!
Not only is it impossible to stop the mind from wandering - it's crazy to think you can. A wandering mind means your attention is not on the present. Your attention has strayed from the focus of awareness. Every one of us has a mind that wanders, to some degree. One way to get the mind to wander less and be aware, when it does wander, is through the practice of mindfulness and meditation.
The more you practice meditation, the stronger your concentration and sense of calm will be. Sometimes it’s said that the “wandering thoughts are the weights that train the muscles of the mind”. Every time your mind wanders, in the state of meditation, just bring it back to your focus. It's kind of like doing bicep curls for your brain.
It might help to realize that the only way you can know that your mind is wandering (thinking, fantasies, worries) is when you have to come back into awareness of the present moment. If your mind wanders 100 times, that means it came back at least 99 times, and each of those is an awakening - 99 awakenings in a single meditation! WOW - that's a lot of bicep brain curls! This is really at the core of what meditation is about - those little bicep curls for the brain.
So you can see, with practice, you will be able to hold the present moment a little longer. Each time you are aware of your mind wandering, you are bringing it back to the present moment. Each time you do this is like a bicep curl for the brain. PRactice makes better so keep practicing.