It may seem like common sense that two people teaming up toward joint goals in partnership need to share some similar beliefs and things they value, or else partnership will not go so well. Even so, we need to think a bit about what a belief is, since it doesn't need to pertain to the fine details of what goals they choose together. It may be as simple a mismatch as one partner being much more the optimist of the relationship and the other being far more a pessimist.
They may then, both enjoy beach vacations as a family goal, but when one of them is far more pessimistic, this may get in the way of actually even enjoying success if they do reach the goal, or if one is far more overly optimistic as to be foolish about the goal, or "pie in the sky" in thinking, it may sabotage actually reaching the goal by way of first having a realistic strategy together.
There are many unforeseen incompatibilities of one's beliefs and things of value that need to be explored by a couple, before they ever get together in the first place, and among those are the beliefs held dearest in life, including those pertaining to your personal "life's mission" or "life's purpose." Depending which phrase you like best, there will be "dearest beliefs" that also feed your sense of gender instincts as a man or woman, and these cannot be violated, even for the sake of very admirable "joint goals." Both your personal goals as individuals, and joint goals as a couple must be met in the partnership, for it to last.
For example, he may despise living in the suburbs because they directly interfere with the convenience of excelling at his personal career mission, and neglect of this sabotages his very sense of masculinity. Sexual attraction, and attractiveness, dies as a result and so does the relationship.
She may despise living in the noisy city center, which is unfit for raising children - a major goal of hers - and for the calm needed in her career purpose as a writer and artist. Neglect of this set of beliefs, "cities are noisy," is the death-knell of the relationship, due to a subduing of her femininity and instinctual expression that carries certain "dearly held" beliefs within it.
You have likely encountered many times when there has been a great mismatch between the quality of a partner's beliefs - such as political, religious, or parental style beliefs that are very different from your own. This tends to cause one of the partners to have to work extra hard for them to reach the personal success at their personal, "life's purpose" or "life's mission" on account of sacrifice of it for the "joint goals" of the couple - even when they fully agree with the latter. Which can lead to the resentment of the one doing far more work, energy expenditure, time expenditure, when their personal goals do not simultaneously also carry weight in the "joint goals." And where the partner's personal goals are very similar to the stated "joint goals" of the couple. This often happens when there is codependence in the relationship, and one partner is more of a "bully" about what constitutes "joint goals" than those of the other.
He's a Republican and she's a Democrat. He's Jewish and she's Catholic. He's from the Eastern Seaboard, and she is from the West Coast - all of which carry certain cultural beliefs. It's where you often hear, "you're not with the program," or "get with the program" in a fight, or when at breakup, one of the partners says, "we grew apart" (meaning that the life's goals personally put on hold to sacrifice for the "relationship," were neglected all along by the more narcissistic partner, who bullied the partnership into their personal goals being the same as the supposed, "joint goals.)
Stop this at the beginning, by comparing beliefs in a prospective mate, that are attuned to personal goals, "life's mission" or "life's purpose" in the first place.