Firstly if you think you may have ADHD go and see a doctor for a diagnosis. It's a very common condition and there are a set of well understood and effective treatments.
Second, if you struggle to motivate yourself, maybe reassess what you are working towards. Perhaps the problem is not with you, but rather with what you're trying to make yourself do. There is an almost infinite range of activites available to you, try some new stuff, and then keep trying new stuff until something sticks.
When you really find your passion you won't need to play tricks on yourself to get stuff done, you'll just do it because it's fun and rewarding.
Here's an interesting resource for helping you find out what you are passionate about. Starts by thinking about what is the biggest problem in the world you want to address, then find a career where you can contribute to it (which can also be "earn a lot of money, then donate to charities addressing problem X").
Second, if you struggle to motivate yourself, maybe reassess what you are working towards. Perhaps the problem is not with you, but rather with what you're trying to make yourself do. There is an almost infinite range of activites available to you, try some new stuff, and then keep trying new stuff until something sticks.
When you really find your passion you won't need to play tricks on yourself to get stuff done, you'll just do it because it's fun and rewarding.