Every relationship is different of course, but here's an example of one case:
Neha and Sameer have been in a relationship for five years. Since she’s been in the relationship, Neha has been gradually retreating from a lot of social engagements – she stops spending time with friends and family and devotes all her attention to Sameer. Sameer is very possessive of Neha and demands that she spend all her time with him. He gets jealous if she spends time with anyone else. Neha hates being questioned and finds it easier to be around Sameer rather than face his anger at the end of the day. Sameer controls every aspect of her life. She finds it difficult to break away from the relationship because Sameer threatens to harm her or himself. After many years of unhappiness, Neha realises that she's caught in an abusive relationship.