So, in all seriousness now...if you want to just "cope", then I can't provide anything. If you want to make a difference in your life, though, read on - I'll write this in the context of a career.
First and foremost, you need to work with the boundary condition that you yourself aren't going to change the world or leave a mark. This requires many different people supporting you, and you supporting many different people. Folks like Satya Nadella, Elon Musk, etc didn't make the world a better place themselves. They are the figure heads that represent that accomplishment, but they don't for a moment believe they achieved this by themselves.
That said, you need to sit down and figure out where your passion or interests lie and how that intersects with what you could reasonably be good at. The key point here is not what you are currently good at, but what you feel you could train yourself to be good at. Also think outside the box or tangentially. For example, I am a chemist by training, but figured out how this intersects with a software related career and took a divergent route.
From there, set up a plan after research and see if it fits into your goal's time domain. If not, rinse and repeat, or level set your expectations.
Once you've established, amicably to yourself, the above, start taking baby steps - you will fall...a lot...but the key point is to get up, learn from your experience, and apply it to your future activities.
As you take your first steps, realize that achieving your goals isn't a single sudden event. It takes many repeated events of taking small responsibilities, delivering on them, and proving yourself to people around you. Remember that trust, respect, and confidence are earned over time with repeated success.
As you gain experience, rapport, trust, and respect, you will invariably be given more responsibility and individual decision making opportunities which require other people to support you. It's at this point where you have ownership and responsibility of decision making where you will also start to have the freedom to make proposals and ideas which start to impact the world...sometimes in small ways, other times in big ways. This could be a project proposal in a company you work for, or collaborating with peers with mutual respect and trust you decide to spin off a venture with, or taking your successes and training the next generation of industry leaders.
This is time consuming hard work with a lot of successes and failures along the way. But, the important thing is learn from your mistakes, drop the mindset of wallowing in failure and always be figuring out how to rectify your failures and how to prevent them from happening again.
To be super blunt, the notion of "coping" with mediocrity will never get you out of mediocrity. You haven't achieved some subjective goal you set for yourself. Boohoo. Instead of figuring out how to cope with that, spend time and effort figuring out how to reset your expectations properly and taking small but concrete steps in achieving reasonable goals from within the boundary of reset expectations.
Last - don't set a life goal that is 100% achievable. Set one that is hard and always be striving for it. When people achieve their goals, that tends to be a moment where a lot of people's personal growth stops.
