Because inside every small thing is the seed for bigger things.
All the big things you can see around you mostly evolved from smaller things. Every successful company you see out there started from ground zero. And then they became small, before growing bigger.
If you take your eyes off the small thing that is growing organically in your hands and start chasing big things, you would just miss your miracle moment by several miles. Sure, it is not fun watching small things grow, it can be discouraging and dis-heartening but if we stick with it and keep pushing out, we will connect with the big-ness embedded within.
Inside every small thing is the seed for something bigger and better. If we respect it and take it serious enough, it will give us everything we need.