Wow! So much wisdom here! Thanks bgcat57!
Except by chance, I don't believe you can have any decent, rewarding relationship unless you expect it to be long-term, and behave accordingly. Many don't turn out to be forever, but to expect anything less is a guarantee that it won't last.
Since everyone's experience is different, here are the rules we used:
1/ Accept each other. There should be as few rules, expectations, and judgements as possible. Let your partner be himself, and let him grow. Give him room to breathe. This is the true, deep form of compromise.
2/ Whatever you do, make sure you are proud of it, open about it, and have no regrets. The harder, scarier, or more painful something is, the more important it is to apply this rule. This is half of the essential trust-building.
3/ There is no such thing as too much communication. Again, The harder, scarier, or more painful something is to say, the more important that you talk a lot about it. This is the other half of trust-building.
4/ Each partner must always take care of himself mentally and phyiscally, and carry his weight in the relationship. One can't carry the other forever - that just drowns both.
5/ Every day, each partner should wake up and ask "is this the person I want to be with?" If the answer is yes, then he has to SHOW it. Every day. Never stop dating.
Can't say I've followed these perfectly, but I certainly still believe them.
bgcat57 saidOpposites may attract, but they don't stay together. You have to have more things in common than things that are different.
You have to be willing to compromise equally. (That means that you BOTH have to agree on what 'equally' means.)
You have to communicate regularly, openly and honestly. Every time either of you say "Well, I can't tell him that" it's another nail in the coffin.
You have to be able to weather a storm together. This is the test of any relationship. It is the very thing that strengthens or weakens a relationship in the way it's handled by both. Think about it this way: If he literally lost a leg, would you stay with him, or conversely, would he stay with you if the situation were reversed.
You have to be on the same page in life logistics. Finance, work, responsibilities, friendships, family, etc. This doesn't mean you have to be in the same place regarding these items, but you must fully accept each other's views, status, and ideas regarding them.
If you think there are things about him that will change, that you want to change, that will need to change: get out now! The only personal changing that should be done in a relationship that you're responsible for is yourself. If you don't love him as he is, then it won't work. The corollary to that is that if he does change (and it isn't a self destructive action) then you need to roll with it.
If the relationship doesn't seem great to begin with, it's not likely to improve. It can improve, but it's better to start with something good and watch it get better than to be in something mediocre and expect it to improve without a LOT of work from BOTH parties.
It's far less about the luck in finding the right person than in recognizing that person when he's right in front of you (whether it's literally or virtually).
Lastly, look at what makes your existing long term relationships (non romantic; friends etc.) work. This will tell you more about what you actually need versus what you think you want. Guys often have a wish list that doesn't include what they actually need. You can choose clothing by color alone, but without taking the size into account, you're going to end up with a lot of clothes you can't wear.