I'm an INFP chick currently with an ISTJ guy. We've been together for about 2 years now, but lately (meaning the last few months) I've been unsatisfied with the relationship. I feel like he doesn't understand me and what I need, even though I understand him. It's really hard to tell him how I feel because I've tried so many times the best ways i know how (through letters, mostly, and once with a talk) but he never changes the way he does things. It's like talking to a brick wall.
This guy has been one of my closest friends for years, and in all these years he has never changed. He still acts like a 20-year-old kid. I'm 19 and sometimes feel like his mother, which I really don't think is good when I'm trying to have a fun, romantic relationship.
So my question is... As two almost completely opposite personalities, are we just destined not to work in the long run?
Expecting change and growth from an ISTJ is like expecting forgiveness from a brick wall.
The key here to remember is that you two are almost polar opposites. Where your decisions and reasons are made based on personal values that have an extreme importance to you, his decisions are made on traditional ways of doing things that he knows are tried and true, which is of equally great importance to him. Where your values aren't necessarily rooted in tradition, his traditions aren't necessarily rooted in personal values.
So from an INFP's perspective, ISTJs are illogically rigid over things that shouldn't be issues (ironically, they see us in much the same way), and they have a lot of trouble seeing other ways to do things. Compare that to how we can see a million different ways to do things, and... yeah. I've heard of this type working before though, and I also know a couple that's failing miserably because the INFP is unhealthy.
So I think the biggest issue you'll have at the core of your relationship is the chronic feeling of emotional unfulfillment. At the same time, you need to look at the things he does to provide for you as his way of expressing his love and loyalty to you. ISTJs I know of tend to do it by being responsible about the bills and providing you with things you need to survive, which for an INFP can be easily overlooked. We're notorious about getting lost up in the clouds, right?
But he does those things because it's his way of showing his love for you. When ISTJs get asked if they love the person, most of the ones I've heard of tend to have an "I'm still here, aren't I?" response. To an INFP that's a weird reaction. We consider that to be the bare minimum of a relationship and not a valid expression of devotion. But to them that means everything. They really care, they just show it in extremely utilitarian ways.
So you'll feel lonely at times. But that's the worst it'll get, other than being frustrated by his rigidity in problem-solving and being bored, like you said. ISTJs aren't the most exciting people to INFPs. The thing to look at to make the relationship work is if you can be happy knowing that he'll love you by working to provide for you and take care of you in the ways that are important to him.
Like one example I heard of was when the ISTJ had died and the partner started trying to get everything taken care of after the death, only to find out that he'd already arranged all of the insurance stuff, organized all of the funeral and cemetery payments, and dealt with all of the finances to make sure the wife had a stable financial arrangement for a good number of years.
That's how they show love, and they mean it. If you ever challenged their love for you, they'd get really offended. It's just a kind of love language that you need to learn, something you need to sort of figure out to really appreciate.
It's sort of sacrificing emotional care for physical and financial care, but the love is exactly the same. So the real question is do you could be satisfied by the way he expresses himself to you?