Attention is a mental muscle, and can be strengthened with the right practice. The basic move to enhance concentration in the mental gym: put your focus on a chosen target, like your breath. When it wanders away (and it will), notice that your mind has wandered. This requires mindfulness, the ability to observe our thoughts without getting caught up in them.

To Strengthen Your Attention Span, Stop Overtaxing It - Daniel Goleman - Harvard Business Review