If you want to go fast, go alone. If you want to go far, go together.
The periods in which I've done the most tangible work have been alone - by tangible work I mean work that you can physically see (in cases hear) or hold in your hands.
If you were to write a book, that's a tangible piece of work that can be held in your hands, a product of you writing one word at a time to fill a manuscript - a product of hours spent.
When you are alone, with the noise removed, you can simply put in more hours towards that tangible work.
This can be extremely valuable, because in many cases those hours spent are necessary and cannot be worked around.
On the other hand, the periods in which I've made the most progress have been in the company of others, or as part of a team.
People all have their own skill set, perspective, and experience, which can rapidly accelerate progress - and that's aside from them potentially adding an "extra pair of hands".
My single biggest lesson this year (joint with lesson 2) has been to listen, learn, and in cases be mentored by others - those with skills that you lack, those with experiences that you've yet to encounter, those who see the world through a different lens to your own.
Yes, put in the hours to get the necessary "tangible work" done, but use that as the foundation to be lifted by others around you.