When we've been with someone for years it almost feels like we can finish their sentences and complete their thoughts. Although that might sound cute, it can also be detrimental to the longevity of your relationship. Mind reading and making assumptions is a learned behavior that can get in the way of effectively being able to communicate with your partner. It's one thing to know your lover well, but it's another to assume what or why they've done something and not allow them the chance to respond for themselves. When we're frustrated we sometimes have a tendency to lean towards negative assumptions and punish our counterparts without ever giving them a chance to provide their true perspective. Either way, making assumptions and trying to read your partner's mind can lead you down a path to communication destruction.
In order to ensure effective communication, stop yourself from trying to read their mind and confirm with your partner that what you're understanding is correct. Not only will they appreciate the consideration, but you'll see a decline in unnecessary arguments. Knowing this is easier said than done, take your time and keep reminding yourself that it's easier to ask and confirm than to assume and argue.