When people are in love, they tend to overlook some of their partners' flaws and make up excuses for their bad behavior.

However, several experts believe that people need to be tough on their assessment of their partners, otherwise they could end up with just heartache and problems. One of the red flags in any relationship is having a partner who is rude or mean to strangers, according to the Huffington Post.

He or she might be cordial to you, your friends and family, but if they can't be nice to strangers, then it's a bad sign. "Pay attention to the small things: how they interact with the server at the restaurant, the Lyft driver, or the stranger at Trader Joe's. Harsh treatment of strangers can say a lot about how they view others. Note that bad behavior toward strangers typically evolves into how they'll eventually treat you," warned clinical psychologist Ryan Howes.

It's even more alarming if the partner refuses to spend time with your family and friends.  For therapist Elisabeth LaMotte, it is a "meaningful concern" when a partner introduces you to his or her circle but completely avoids any social gatherings on your side.

"Ideally, it should flow both ways — with invitations to join your significant other's life milestones and occasions and also with demonstrations of interest and enthusiasm about your friendships, family and life events. If you notice that you are always making excuses for why your partner is never free to join you in social settings, this may be cause for an honest conversation," she said.

Another thing to watch out for is a partner who is often badmouthing their exes. In doing so, the partner is showing that he or she does not hold himself or herself accountable for any wrongdoing and likes to point their fingers on someone else.

"This is a red flag that they haven't done any introspection about what their behavior contributed to the deterioration of these previous relationships," explained psychologist and dating coach Samantha Rodman. "No relationship ends only because of one person's behavior, and if your partner acts victimized by their exes, one day they will likely play the victim card in their relationship with you."

It is also wrong for a partner to refuse to apologize. Marriage and family therapist Winifred M. Reilly said that a partner might make up for their mistakes by being extra nice after a fight, but being able to verbally apologize is a sign of maturity. "It says, 'I'm willing to be accountable. I can admit my mistakes.' The red flag here is that over time, your relationship will suffer if the only person owning up to misdeeds is you," she said.

Lastly, a strong gut-feel of something being wrong is a red flag that must be addressed. Tracy Malone, a relationship expert on YouTube, told The Independent that victims often see different behaviors as time and abuse goes on.

"Actions speak louder than words. If the date says one thing and does another, look deep into yourself and tell yourself it will only get worse and walk away," she said. "If you are dating someone who tries to rush a relationship without giving you time to get to know them properly, slow it down yourself and take control. If they are not patient with this request, you get out."

"Never be rushed, even if it feels good. A soulmate will be kind and patient, while abusers rush to confuse victims and to control. If you prove hard to control quickly, an abuser will back off, and you will save yourself heartache," Malone added.