There’s a line in any relationship between things that are unnecessary to disclose to your partner and the small transgressions that just feel easier to keep hidden.
Errant sexual fantasies about other people or doubts about the relationship that you haven’t yet resolved are best kept private unless they materialize they into a real issue that you can address to your partner.
Then there are thoughts and behaviors that require transparency, but simply become easier to conceal because ‘making them into an issue’ would blow things out of proportion. Maybe you get back in touch with an ex in a platonic way, or conceal from your partner that you once had a relationship — or a fling — with a friend. Perhaps you have a habit — smoking, gambling, going to strip clubs — that you find harmless to keep in the dark, because you can handle it, and what your partner doesn’t know can’t hurt them.
Perhaps you’ve managed to convince yourself that you’re protecting your partner by keeping these secrets from them.
But when you behave this way, you’ve entered dangerous territory, and it won’t be long before the accumulation and maintenance of your lies begins to threaten the relationship. Lying to your partner becomes your primary mental activity — measuring your transgressions, keeping them out of your partner’s sight, and speculating about whether or not your partner knows becomes your principal form of mental participation in the relationship.
You must also constantly self-debate whether the things you are hiding are small enough to keep hidden of if they’ve gotten out of control. You will enter the realm of self-deception, where you wind up assuring yourself that something you really aren’t comfortable with is okay. Self-deception is the most dangerous path of all, as it erodes your trust in yourself and begins to cast doubt on everything you find meaning in or enjoy — particularly towards the relationship itself.
Keeping secrets will poison you from the inside. Even if the relationship is good, your time together is asterisked by your lying, and the asterisks will grow to overshadow the story of your happiness with your partner.
It takes a tremendous amount of discipline to be honest with your partner. Heck, it takes a lot of discipline to be honest to yourself. But if you aren’t willing to maintain your integrity and either refrain from or disclose your less-than-flattering behaviors, your relationship is going to fall ill under the strain, and sick things can die.