How does one know if they are in a healthy relationship?
In a healthy relationship, you will be happy most of the time, trusting of the person you are with, trusted by your partner, and able to express yourself without fear of judgment.
A healthy relationship is also one where money is not used as a weapon, faithfulness is present and abuse (emotional, sexual and physical) is absent. Respect, consideration and love are also signs of a healthy relationship.
As cliche as it is, communication is key, even if it means deciding what not to talk about. For example, I was in an open relationship that was quite healthy because we didn’t talk about our separate sex lives. We were both truly happy with the setup, but we didn’t want to think about the other person in bed with someone else. It only ended because our lives were going in different directions. You need to be able to talk about anything and everything with each other. Communication is probably the biggest factor in a healthy romantic relationship.
Another thing is that you need to be able to be yourself effortlessly with someone. This may seem obvious but it actually tends not to be, especially in relationships between young people. If you can be yourself at your weirdest and not worry about what your partner thinks about it, you’re in a beautifully healthy relationship. Basically what I’m saying here is that you really ought to date someone who is like a best friend with whom you’re romantically involved (though that doesn’t mean get romantically involved with your best friend of whatever sex you’re attracted to; there’s a difference between dating someone whom you can also be friends with, and dating one of your actual platonic friends).
Lastly, take people at face value. If you spend all your time worrying about them cheating on you, or being possessive over them, not only are you wasting your time, but you’re making them less inclined to stay with you (unless they treat you the same way, which also isn’t healthy). If someone is going to cheat on you, they’re going to do it no matter how protective you are over them. You could be ruining a potentially wonderful relationship with all the excessive hovering. You have to trust each other, but not necessarily in a way that they have to earn that trust — you have to acknowledge that your past relationships do not define your current one. Take people as they are, not as you think they might be.
If you meet all these things in your relationship, I’d say it’s pretty solid.