One-track mind

/wˈɒntɹˈak mˈaɪnd/

/wˈʌntɹˈæk mˈaɪnd/

One-track mind

used of a person whose mind is busy with the thought of a particular person or thing and cannot think of anyone or anything else

Examples

1. For 45 years of my life, I've had a one-track mind.

2. At the end of the day, I feel like there's a very distinct, slight difference between me and the majority of what's out there, which is not being at the mercy of this being my livelihood, gives me the ability to have a one-track mind, which is to bring you guys the most value possible with no expectation in return.