It sounds crazy, I know. Because what we believe that our thoughts generate automatically. Yeah, it's true. But we also can make some input and keep the flow. There are many possible ways by which we can make it happen.
You may wonder, why we need so! Well, think about how your thought process works, what you usually think, what makes you feel worries, what thoughts are useful, and what are not. You will get an idea of why you should make some input on this process and just not let it flow like that.
After realizing the necessity of our 'input' we should learn some basics about how to make the input!
Be mindful, be present at the moment. This is what you need most if you want to create your personal thoughts. When you focus on what is happening, how you are feeling, and observe your surroundings; that's when you block your unnecessary thoughts about worries. And it gives you a space to create your own.
Also, you have to learn how to detach yourself from chaos. Sometimes, many things go all together in our minds and we can't decide what to focus on. Practice to pause/break in between thoughts and take yourself out from this chain of thoughts.
Most importantly, practice positivity. Whenever you find your thoughts are flowing scattered, input some positive thoughts there. Think about something wonderful you have done, think about any imaginary happy future, how you can add more value to your life. Replace positive thoughts in your mind.
What we need to understand is, our surroundings should not decide our thought process. We always should be the one, what we want to be in our head. And only creating our own thoughts can give us that power!