Meditation. Or Awareness Meditation to be precise. It enables me to regain control over my mind, because I get distracted really fast. It really helps sorting things out, taking a step back and getting an overview where I actually am and if what I'm doing right now is actually relevant/has priority. I mostly find that it's not, so I have to return to the important stuff.

For those interested: meditation sounds weird, even obvious at first or you just don't get what's it all about. You actually have to practice meditation for a long time and study the concepts until you start to understand what all these phrases and talking means. Behind them lies great wisdom/huge amount of concepts which is easily underestimated. So don't be frustrated too much if you don't feel it working right away. Be assured I've been there too. Also don't start with meditations like 'just stop thinking or think nothing' because in my opinion this is highly complex shit and frustrating at first. Start with awareness or breathing meditations or even get an app to support your daily habit.