I think you want to start by answering two questions? 1) what is "the world"? Is it the planet? (Your change needs to apply to different ideologies, languages,

I think you want to start by answering two questions? 1) what is "the world"? Is it the planet? (Your change needs to apply to different ideologies, languages, cultures - like, say, a medical advance.) Is it national (affecting just your country), like say translating media into your local language, reforming politics, or education. Perhaps it's niche, like improving accessibility for the disabled, perhaps it's building a local free-upcycle site so those with stuff to get rid of connect with those who need (like say a Facebook group.) How many people do you need to touch to consider your effort a success? 10? A million? A billion? Question 2 - why? Are you after fame? Fortune? Penance? Legacy? Understanding your root motivation here will be very useful to you. Does it matter if you change the world, but die poor and young? Does it matter if you're anonymous? Does it matter that the world knows it has changed? Are you prepared to sacrifice your life to change the world for others? Nelson Mandela spent 27 years in prison, but became the inspiration for a nation. Is it better to improve one life at a time, by say installing solar panels or attempt to solve climate change (and likely fail?) In others words is it more important to aim high, and fail, or aim lower and succeed. Figuring out your root motivations will help you understand what it really is you want to do, and at what cost. Defining parameters for success, and failure, will help you evaluate ideas. Good luck.