Yes handwriting comes naturally, so it reveals a person's nature. When I am writing I focus on the content rather than the formations of the letters. I am less conscious about the strokes and more conscious about the framing of sentence, usage of appropriate words, spelling, meaning of the sentence etc. But the handwriting is unique for everyone, so it means that something governs the handwriting style.
It comes almost similar every time I write so it is a natural way of my writing. It represents all those things that we do naturally.
The science of studying the relation between handwriting and personality is called Graphology.