However, there's good news. We can build our capacity to focus for intense periods. There are two ways to do this: 1) by constantly practicing, holding ourselves accountable and no getting distracted. This is hard. Or 2) one of the other ways that we can build our capacity for sustained attention is through meditation.
If you're like me, you have no interest in practicing traditional meditation, but meditation has been described as 'push ups for the brain'. It builds the 'strength' of our ability to focus and our performance is almost solely dependent on our ability to focus our attention on the right things at the right time.
100 breaths meditation is a quick and practical way to build focus.
Find a comfortable position (you can close your eyes or open them - it doesn't matter) and then start counting your breathes backward from 100 to zero. You'll get intruding thoughts as you do this, but simply acknowledge them, put them to the side and get back to your counting. You'll find that as you practice, you'll get better at shutting out distractions.
The bonus is that this simple 15 min exercise is one of the best ways to also decrease the stress response and will help you get to sleep at night, if your mind be hyper-active.