If you want to be able to focus on something for a long time, there is no other way but through practice. You can use the awareness of your breath flowing in and out of your nose. Gradually practice for 1 minute, 2 minutes, or several minutes, and you will become more proficient through your training. A quiet place, when your stomach is not too full, and when you are not under the influence of alcohol—these are conditions that help make your practice more effective. If you are interested in learning more, please search for the term "Anapanasati."