You need to be honest in your online profile to attract the right person for you. However, oversharing will turn people off. So how honest should you be?
If you know you have a core personality trait that has frequently prevented you from creating harmony with a certain type of personality, then you need to avoid that type of personality in romantic partners. You should absolutely write about it in your profile, just make sure you state it positively.
For example, if you have strong opinions and enjoy debating them you should say something like: “I’m looking for someone who enjoys lively conversation and is comfortable with a good debate.” That will scare away anyone who doesn’t do well with that sort of conversation, and you won’t waste any time with the wrong person.
It is not necessary to air all your dirty laundry though. If you’ve just been through a devastating divorce that wreaked havoc on your life, lost your job and/or moved back in with your parents, had a mental breakdown, have been grieving the death of a loved one, or any similar negative life experience there is no need to reveal it in your profile. Furthermore, it’s inappropriate to do so. Deeply personal information and dark family dysfunctions are better left revealed as you get closer and trust is established.
If someone isn’t going to meet you then it’s none of their business what your problems and shortcomings are. Don’t display them. If you feel comfortable being an open book than you really need to strengthen your boundaries.