We all look at the world differently. Every single one of us had different upbringings, different experiences, different genes, and we do different things. When we see what someone else is doing, many of us tend to assign our values to it. We say essentially “well if that were me, then I would have acted differently,” whether it is what we actually say or not. Assumptions like this can be made when starting a job, because maybe we assume that our new co-workers have all the same philosophies as us. They can happen entering a marriage, because maybe we assume that the other person has the exact same definition of marriage as us. They can happen at a restaurant, because maybe we assume that their definition of healthy or of clean is the same as ours. The number of possibilities is endless.
Spend time really noticing how often you make such assumptions. Then, decide what they are doing for you. I contend that assumptions like this really serve to hold us back. They cause things like being unsuccessful at work and failed marriages, and all it would have taken is a little bit more discussion up front. To avoid things like this from happening, ask people what they really mean when describing something that is important to you, it tends to make for great discussion anyway because it is about feelings instead of being about stories.
Assumptions are a slippery slope. Make a resolution to get them out of your life and watch what happens.