"This can put a lasting strain on the relationship," Rori Sassoon, a professional matchmaker and co-founder of Platinum Poire, a matchmaking service, tells Romper by email. "A strong relationship is built on friendship and shared memories. If you don’t want to spend your down time with this person, what are you doing?"

Of course, if you occasionally travel with siblings, friends, or even alone rather than with your partner, that probably doesn't mean that your relationship is doomed. However, if you regularly (or always) vacation without your partner, that might not be a very good sign.

Big life events like birthdays, anniversaries, promotions, and more deserve to be celebrated, but if you celebrate friends' and family members' big moments alone or choose not to celebrate your joint life events (like anniversaries), that might indicate that things between the two of you aren't actually going to work out.

"Birthdays, anniversaries, weddings, and other important life events usually involve bringing along a 'plus one,'" Jonathan Bennett, a certified counselor, life coach, and dating and relationship coach, tells Romper via email. "If your partner consistently attends those and similar events alone, it’s a sign you’re not an important part of [their] life. It also could mean [they] doesn’t want you to meet [their] family and friends."

"Parenting separately, undermining each other, making one parent the 'bad guy' and the other the 'fun one' not only makes managing the kids harder (they get manipulative with their behavior), but it builds resentment and increases isolation," Parisi says. "Parenting together as a team has it’s drawbacks (you don’t always agree on an approach), but you have a teammate and can lean on each other for support. The 'go ask your mother/father' or 'just wait until I tell your mother/father' makes one of you the bad guy, automatically putting you on opposite sides."

Working together keeps you on the same sides, where you belong, rather than making you unnecessary adversaries.

Whether it's a potentially serious and bad news-laden medical appointment or a celebratory appointment filled with good news, you should probably have your partner by your side.

"You shouldn’t have to go to medical appointments you’re worried about by yourself, and your partner should be your ride home after surgery," Parisi says. "You partner should share in the joy of great news (sonogram, remission) and also be there to provide support if the news isn’t great. Your partner can ask questions, help retain the information discussed if you’re in panic mode, or just hold your hand so you’re not alone and scared. Not to mention, a medical concern that effects one of you really effects both of you. Going through those things alone creates emotional distance and feelings of isolation."

And that feeling of isolation can make it difficult for your relationship to ultimately succeed.

Doing your own thing isn't bad — it's totally fine to have your own hobbies. But if all of your hobbies are individual, that might mean that something's not quite right. "Whether it’s painting, tennis or cooking, too many hobbies that a couple does separately may be a problem," Vikki Ziegler, a relationship expert, divorce attorney, author of The Pre-Marital Planner, and star of Bravo TV’s former show, Untying the Knot, tells Romper by email. "While independence in a relationship is healthy, always doing separate things can draw a wedge between the two. Even if you’re not crazy about your partner’s hobbies, it’s important to try and take an interest in them, or find a few hobbies you can enjoy doing together."

Family events should ideally be attended together, not apart. If the two of you won't attend the other's family events (or won't bring the other with you), that could point to a potential issue later on down the line. "If they miss a family dinner here or there, that’s one thing," Parisi says. "Not going with you to weddings, funerals, reunions, birthdays, holidays, whatever is a big deal in your family, shows at the very least a lack of interest and investment in the people you love. (The reverse is true as well!) To not have your partner be a part of special occasions, memories, those inside jokes…that adds up over time."

Make an effort to know their family and spend time with them. It not only shows them that you care about becoming a part of the family, but also that you care about your partner and what's important to them.

"If your partner’s employer offers social events that involve families and significant others and you’re not invited, it says a lot about [their] commitment level to you," Bennett says. "If the relationship is solid, [they] should want to show you off at work! If you’re not invited, it’s a red flag."

The reverse can be true as well. If you don't want to bring your partner to work-related social events, you might want to ask yourself some questions about if you see the relationship lasting long-term.

No relationship is perfect — there's bound to be some conflict from time to time, but dealing with it alone might not be the best strategy if you're hoping your relationship will last.

"If you’re processing your conflicts separately (I mean only separately, not like venting to a friend and then coming back to your partner for a calm discussion), it means that you’re not reaching a resolution together," Parisi says. "You’re not finding a compromise, or making changes so that everyone’s needs are getting met as much as possible. Without discussing your conflicts, how do you know what went wrong, is going wrong, or how to do better in the future? You may think you’re saving yourself the hassle of an uncomfortable discussion, but for so many couples, resentments are just piling up...which leads to an explosion of some sort."

Talking to each other is the only way to know that you're on the same page and able to work through things together. Working through conflict as a team can bring you closer together, as well.

Trying new things is great, but only trying new things on your own and sticking to the same old, same old with your partner isn't. "You end up having these funny, horrible, boring, awesome, surprising new experiences and they don’t (or vice versa) and too many of those starts to feel like living totally separate lives," Parisi says. "Your partner has done a laundry list of things that you haven’t, have experiences you don’t share, and the excitement isn’t associated with your partner, but rather the opposite."

Though it is, of course, OK and even good to do things with friends, siblings, or even alone without your partner present, you shouldn't underestimate the importance of doing things together. Parisi says that focusing on doing things together is more important than focusing on what you shouldn't be doing apart. But if you want your relationship to last and be successful, making sure that you're keeping your connection strong and not doing things that can hurt your bond is of the utmost importance.

Check out Romper's new video series, Bearing The Motherload, where disagreeing parents from different sides of an issue sit down with a mediator and talk about how to support (and not judge) each other’s parenting perspectives. New episodes air Mondays on Facebook.