Relationships and marriage are hard! There are some obvious things that would break a relationship, such as physically cheating on your partner, or you and your partner having radically different values, or maybe one wants kids and other is decidedly child-free.
1. Putting your wants and needs above your partners
2. Taking your partner for granted
3. Emotional cheating
4. Not standing up for your partner
5. Lying to your partner — even about stupid things