Understanding relationships is extremely important. Relationships don't develop overnight. But small mistakes can shake the foundation of your relationship in a single day. Though relationships aren't fragile, they are sensitive. Small mistakes can gradually ruin relationships. Even if there's no breakup, it can have a negative impact on the relationship.
How well you're doing in your relationship should be expressed repeatedly. Your partner should always be made to feel special. Similarly, there are 4 things that should never be said to your partner. Don't say them even by mistake. These won't just break your partner's heart, but will also ruin the relationship.
'I made a mistake thinking of you as my life partner'

Such words hurt your partner's feelings. Expressing regret about the relationship—such words shouldn't be said even during fights. Even after fights and misunderstandings are resolved, such words leave a lasting impact. This weakens the foundation of the relationship and can destroy your partner's trust in you.
Taunting about your partner's financial situation

Your partner may not be financially well-off. You may earn money that your partner doesn't. But never criticize your partner's financial situation. Insulting or mocking someone about money hurts their self-respect. Besides, your partner may feel that you're not happy in this relationship. And if this continues day after day, the relationship is bound to break.
Insulting family or friends

Everyone's mentality isn't the same. But family, friends, and loved ones are close people. Whatever they're like, don't speak badly about them. If you insult your partner's close people, you'll become small in your partner's eyes. This will increase distance between you two and create resentment within.
Making fun of your partner's weaknesses

Everyone has some weaknesses about something or other. Many people suffer from inferiority complexes even about small things. But you should never joke about these. This makes your partner feel humiliated and reduces their self-confidence. Instead, if you know the reason for your partner's weakness or inferiority complex, try to help solve that problem. Stand by your partner and give them reassurance.