When you cook, do you measure quantities or guess ? ?

When one starts cooking a  recipe by following step wise .
But after cooking the same things several times,  one can 
begin experimenting by changing ingredients or the amounts
of ingredients. That is how one will  learn  about  flavors and seasonings work together.
 Next step is that if one has done a  lot of  cooking, then 
  when one comes across a  new recipe book.
 One can  immediately think of substitutions and alterations 
to the original recipe that would make it more palatable to
your  own  taste.
Have  you ever guessed the amount of people in a room, the
size of something or how long it will take you to get from one place to another, you've practiced estimation. Estimation is 
a mathematical…
The daily day to day cooking, like making tea, most like to measure and make to get the same taste.
Then about making dough, all have a measurement in the
flour tin and may be calculating, for 2 persons so much and 
for 2 extra guest, this much. Making dal, rice , all may be following a source of measurement, so that there is no wastage.
All try to contribute your views , so that we can learn from others tips.
All when baking prefer to follow the recipe  to the exact measurement. Even if planning to make Idlis, Dhoklas and
Dosas, does one follow measurement or is it guess work ?