The question

The question was, "Did you choose or did you just decide that I matter to you?"

My answer was, it is a choice. They said that to them it was not a choice but a decision.

So, I had to look it up.

To choose and to decide are almost the same thing.

choose
verb, chose; cho sen or (Obsolete) chose; choos ing.
–verb (used with object)

1.to select from a number of possibilities; pick by preference: She chose Sunday for her departure.Dictionary.com Unabridged (v 1.1)Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

decide
verb, -cided, -ciding.
–verb (used with object)

1.to solve or conclude (a question, controversy, or struggle) by giving victory to one side: The judge decided the case in favor of the plaintiff.
Dictionary.com Unabridged (v 1.1)Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

I didn't and don't like either of those options. I mean, choosing is as if there was another option that might have been better--like picking what shirt to wear in the morning. And a decision is the weight of more than one equal option.

"Did you choose or did you just decide that I matter to you?"

Neither. You matter because you matter.

It is.

It's a constant, like water is wet and the sky is blue. Even when water is steam you still get wet and even when the sky is overcast it is still blue behind the clouds.

Which means that we had no say in the matter at all, it was serendipitious.

serendipity  –noun

1.an aptitude for making desirable discoveries by accident.
2.good fortune; luck: the serendipity of getting the first job she applied for.
Dictionary.com Unabridged (v 1.1)Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

How we treat each other from that point on becomes the choice/decision factors. I can choose to call you, or wait for you to call me. I can decide if I want to spend Friday night with you or I can decide to spend it with other friends.

So, I am changing my answer to you, neither.

You were one big desirable discovery I made by accident.

Apparently I'm good at that.
Looks like you are, too.

(Thankfully.)