Are you...

[Bri]

Impulsive I guess. But are these two things mutually exclusive? They're not polar opposites of each other or anything.

I had to look at a dictionary definition, and I'm still struggling.

I guess it depends on the situation? I'm normally loathe to make the first move or one for spontaneity, but in a few situations I do jump in (normally for a friend) without thinking of the long-term consequences.

I will compulsively write a shopping list for my weekly shop, but impulsively purchase something that wasn't on the list that I fancied when I saw it. I think that's an example that everyone can relate to that shows how the two coexist very naturally.

True!! This is me. That's why I have Bert go instead. He follows the list.