Assumptions are a serious problem in relationship between human beings. If we want to deal with them we should start from the beginning ...
Everybody has some assumptions. We acquire them almost since the moment of our birth. Most of them descended from our childhood. Let’s take Jane as an example - mother of two teenage children - Julia and Jakob. Jane remembers that in her teenage years she always washed dishes after every dinner and prepared supper for the whole family every Saturday and Sunday. Julia is a teenager, so Jane assumed that her daughter will act similarly to her and wash the dishes after every dinner. Same thing goes with Jakob - Jane assumed that he should voluntarily prepare supper every Saturday and Sunday. Jane doesn't make those activities childrens obligation, she just assumed her children would "do their thing" automatically. In conclusion, those are just two simple assumptions Jane brought from her childhood. What's coming next?
The beginnings are rather innocent and almost impossible to notice. Jane asks Julia to wash the dishes and Jakob to prepare the meal. They obediently do the things she asked and she's pleased while seeing the results. This part might be repeated multiple times. Once in a while one of the kids won't do their duty and the problem starts to develop. Jane stops asking her children to do their (in mother’s opinion) duty and the frustration loop starts. Children won't do the work because they don't even know it's their obligation. Jane is accumulating anger because she thinks her kids are lazy and don't obey her orders. She's frustrated because her children don't stand up to her expectations. From time to time Jane explodes with her suppressed anger collected through few days or weeks. Is there a problem with communication ? Definitely. Is it possible to solve the problem? Yes sir!
The solution to the problem is quite easy. You just have to make Jane realize one of the basic principles - if you won't ask someone to do something you CAN'T expect them to do that. The principle is obvious but the persuasion part probably won't be easy. Jane is emotionally attached to her assumptions. She would in all probability respond with words like "but (name of a person) should (name of an activity) because (name of a reason)". It might sound "but Julia should wash the dishes because it's normal for a young girl like her" or "but Jakob is supposed to prepare the supper because he should help his parents". The sentence doesn't really matter. Whatever Jane would say is brought directly from her assumptions and system of values. She truly believes that whatever are her assumptions it's how the world should work. If she asks her husband to buy some vegetables and he won't buy tomatoes (which are the instant need in the house at the moment) she also might get angry. Why? Because he didn't do what she expected him to do (even though she didn't ask exactly for the tomatoes).
Everyone should realize that people have numerous assumptions and expectations. Some of them are pretty well established in the norms system (like 'people should wash their hands before eating'), some of them aren't. The major problem emerges in the situation when someone’s assumptions aren't met. The typical result of the situation might be either amazement (when someone acted beyond one's expectations) or anger (below expectations). People must realize that some assumptions are just causing unnecessary arguments.
The bottom line is: you can't expect something from someone without asking him to do it. It's far easier for both sides when someone just asks the other to do things they're expected to do. This way both sides know what's going on and everyone knows what are the expectations towards them so they can meet them and no one gets frustrated because unmet assumptions.
Always ask, never assume
This principle also applies to you. Probably you have some assumptions that aren't met. In time you might become more and more frustrated. Most times frustration leads to unwanted negative emotions so it's better to deal with this regularly instead of amassing the bad feelings. Collection of those feelings would in all probability lead to uncontrolled burst of anger which consequences definitely won't be positive. Instead you should gently ask the other person to do what you expect them to do. You might be struck by this but most likely the other person would be surprised with your request and say that never thought of it. Is it that hard to ask instead of making assumptions ?