Relationships are complex. Point blank. If a relationship isn't difficult, then I hate to break it to you, it isn't real. This isn't meant to scare or insult you, I'm just being honest. Sure, you can have simple human interactions in life, with a coworker or your dentist, for example, but I'm really not referring to the dude who cleans your teeth. I'm talking about the deep connection associated with a romantic partner. I think it's most commonly referred to as love.
Due to these complexities, things can get out of hand. Arguments will ensue, insults will be thrown, jealousy arises, tears are shed. It's natural, it's human, it's life. This is all okay and it's really nothing to be ashamed of. If anything, you should take pride in the efforts you put forth that allow these relationships to become stronger. The question remains however, where does the line get drawn? When does it go from your standard, run-of-the-mill argument to something darker and more destructive?
I think deep down we all know the signs. Hell, I'm sure we can even think back to a time that we've offered someone advice on this very matter, but when you're in it, it's really hard to see clearly. It's important to do your best to keep these in mind. The worst thing in life is wasted time and more often than not, people spend years in these toxic situations because they just don't know any better. These signs are most applicable to romantic relationships, but some can be seen in friendships or family dynamics.
It's pretty common for your significant other to want to keep tabs on your whereabouts, but if it goes beyond the typical, "What are you up to?" text, than you may have a bigger problem on your hands. If every time the two of you aren't together, you're berated with multiple calls and texts that stem from a controlling, paranoid and jealous place, you may want to re-evaluate the situation.
If your significant other uses breaking up as a weapon then you absolutely need to take a step back. Ending a relationship is a huge undertaking that should only be made mention of under serious circumstances. Throwing it around like it's a tiny threat means your S.O. isn't aware of how hurtful they can be, or they're very much aware, but they don't care. The latter lends itself to a bigger problem of sociopathic and manipulative tendencies.
Sex is generally considered a barometer for any relationship, but if the sex only happens at the end of an argument then it's possible that the two of you are using it to fuel something that's not really there. Look, I get it, lust and anger can be very closely aligned, but if you're ONLY have angry sex, that's not healthy. Relationships are nothing if not dynamic and the moment they become a singular thing, it's time to end.
Continuing with sex, it should NEVER be used as a bargaining tool. If you find that your S.O. is only complying sexually after you do something for them (cook, clean, a favor, etc.) then you may want to ask yourself what your relationship is really based on. I know this is a pretty longstanding joke about marriage, but it's really quite sad when you think about it. You shouldn't have to mow the lawn or pick the kids up from school to ignite passion in the bedroom.
I don't enjoy stating the obvious, but this needs to be said for good measure. If arguments every turn violent, there is no justification. You leave. That's it. No counseling, no apologies, no excuses. No, "Well he/she didn't mean to." That's all the smoke in mirrors bullsh-t that the media feeds you about love and relationships. Yes, they're complex, but they should never be dangerous, there's a difference.
If you begin to notice that you're S.O. may be using drugs/alcohol to cope with your relationship issues, that's not a good sign. For example, if you find that the only time they can tolerate you is when they're drinking, then you need to do both of you a favor. A true, healthy love shouldn't need chemical enhancements (unless of course you're at the viagra age, in which case, do you).
If your partner is adept at keeping things from you that are commonly shared with a significant other, you may want to start questioning somethings. If they don't discuss things like financial troubles or family illness, then why are you even together? Isn't the point of a partner to have someone to rely on and confide in? If they aren't talking about these things with you, it's possible they don't think you're capable of handling it and that sort of doubt is insulting and consequently creates and unhealthy dynamic.
Again, I hate stating the obvious, but as I said, sometimes people don't realize these things on their own. If your partner cheats on your regularly, it needs to END. Similar to violence, cheating is never really okay. The difference being that cheating can be excused under the right circumstances. People f-ck up, there's really no way to work around that. Additionally, the idea of monogamy can be very difficult for some people. I'm not suggesting you can't turn the other cheek on a drunken, one-night-stand, but if your S.O. is actively having an affair, or constantly seeking sex and validation outside of the relationship, there's absolutely no question that you should leave. That behavior will never change, at least not if they're with you. I don't believe in, "once a cheater, always a cheater" but I do maintain that if a person is capable of cheating on YOU once, they're capable of cheating on YOU more than once.
If your S.O. tries to eliminate, lessen, or otherwise ruin your other relationships, that's a HUGE red flag. Your partner should want to get to know the people in your life, not steal you from them. This is a huge sign of control issues that's often misconstrued as protective, or sweet. I can assure it's neither of those things. This person is trying to create a situation where you can only depend on them, and once you've lost everyone else, you'll have no choice.
Stemming off of #9, the opinions your friends and family have of your significant other are important. If you find that nobody else in your life likes this person, you may have to wonder if you're being blinded by love or lust. After all, your family most importantly has been there from the beginning and they want the best for you! They have no motivation to manifest reasons your S.O. is wrong for you, remember that when they're trying to tell you how they feel. I know it's easy to get defensive, but you need to open yourself up the possibility that from the outside looking in, you're with a toxic person.