Actually, I'm going to differ here. The pain DOES in fact go away! It doesn't mean that you don't miss her sometimes but it doesn't hurt in the same way as it does in the beginning.
Usually, I find it's more a flood of memory that quite takes your breath away! It can overwhelm you a moment's notice. And you gasp, as IF in pain. But I find that once the tears have welled up, I end up smiling at the end, by thinking about the good stuff.
Personally, I would not tattoo myself in memory of my forever pup. Not because I'm against tattoo's but because its really not necessary. Your pup will always hold a place in your heart, and no tattoo is required to remind you.
If I wanted to make a living legacy, I would take the money spent on the tattoo and donate it instead.
I apologize if I sound preachy! I've had my share of death in the last two years (my daughter, quickly followed by my Sheltie). And I've kinda figured out the coping mechanisms.
Best wishes to you.