You say tomato, he says to-mah-to -- but don't call the whole thing off just yet. Compatibility is all about the big picture, so don't sweat the small stuff like favorite movies or taste in music -- that's just icing on the cake! But before you commit to being in it for the long haul, make sure you see eye-to-eye with your partner on the things that matter.

We asked members of Marie Claire's online community for their long-term compatibility deal breakers. Here's what they said:

Member thetrekhippy said, "For me, both people have to have enough common interests so that you can enjoy spending time together doing those, but enough separate interests that you can enjoy learning about those new things from each other as well as enjoy time you spend apart. If you can sit with that person for at least 40 minutes just doing nothing but like watching shows on the telly or listening to music, and never once feel awkward or uncomfortable, never feel like you 'have to make conversation,' that's a good sign."

You and your partner don't have to parrot each other's hobbies and interests to be compatible, but what's key is taking an interest in what's important to your significant other. That means no eye-rolling when he's off to his monthly golf game, and no exasperated sighing every single time her favorite show is on. Keep an open mind, invite your partner to join you once in a while, and show a genuine interest in what makes them happy.

"For me, there has to be shared basic values, along with nonconflicting lifestyles and goals," said uniquelyme2.

What registers as an important topic or value for you depends on you and your partner, but here's a rule of thumb to follow: If you can't get through watching the nightly news together without calling each other morons, screaming obscenities, threatening breakup, or blaming each other for the recession, a long-term commitment might not be for you. Keep lifestyle in mind as well. Opposites may attract, but they don't often stay together. If your ideal Saturday night consists of Netflix and popcorn, and your partner prefers to party until dawn, one of you will always feel frustrated.

"You better know what you want out of this relationship so I have a clear idea of what to expect," stresses jpwoc. Member shell1130 agrees. "I don't need to know where our relationship is going from the first date, but it's important for me to know whether he eventually wants children or if he has plans to live in another country or travel a lot at some point."

Don't hand him the pre-nup over appetizers on your first date, but do keep your future in mind. Lengthy discussions about children, career plans, location, and other major expectations need to be had before you make a major commitment, whether it's marriage vows or a shared apartment. If you're still in the early stages of dating, make sure you're both aware of how exclusive the relationship is or has potential to be. If you're looking for something serious, you don't want to waste time with someone who's content to casually date for years.