It is good to keep your relationships simple. You don't need to either brag about them in the public nor wash dirty linen in public.
Exposing all the happy moments of your relationship may cause envy and jealousy in others; exposing the bad side of your relationship may make you a laughing stock or a topic of gossip for others.
And then there are certain things that should never be discussed even with friends. Here are they:
You don't need to tell your friends all the details of your ecstasy in bed. If your partner comes to know, he or she may feel embarrassed. Your friends don't need to know all the details of your bed life and how bad or good your partner performs between the sheets.
After a fight with your partner, you may feel like sharing your misery with someone. You want a venting outlet. But no, it isn't advisable to talk about your fights anywhere outside. Also, if our friends are biased and judgmental, they may start viewing your relationship as failure.
If your partner is a financial failure, it is better to talk with him and help him work on it. But if you make fun of him behind his back by sharing such details with your friends, it is unhealthy to your relationship.
You can always talk about the bad phases in your relationships with parents or siblings but it is better to keep your friends out of such conversations as they may simply ask you to breakup.
If your partner had a divorce in the past or several relationship failures in the past, you don't need to tell all that to your friends. They might poison your brain.
If you have any complaints about your partner, talk to him or her about them. If you talk about such things with friends, they may naturally ask you to walk out of the relationships as they think you deserve someone better.