When people get into a relationship, there are often expectations that come into play. It could be fairly reasonable things, like communicating well, or being honest, considering physical safety, or doing what you say you'll do. Or, it could be things that are much more subjective, like a particular style of relationship, sharing the same priorities, or feeling the same way about the connection. When things get rough is when those expectations are "violated" by the person to whom they are being attached, who is often either oblivious at the differences in perspective, or hasn't made any agreement to live according to those expectations.
So, how does one deal with that? One of the ideas I've seen espoused is to dispense with expectations entirely. Frankly, while this sounds good in theory, it seems a bit less connected to reality to be workable. Expectations have some value, as long as they are MUTUAL. They can provide a more predictable landscape within a relationship, which ties in with a sense of safety. Mutual expectations can give direction to a relationship, as people are able to work towards goals and shared perspectives. The key is that word "mutual". Projecting your expectations on others may work out for a while, as coincidence and NRE play together to buffer differences, but there will come a point where, unless you actually agree on what expectations are part of your relationship, things will hit a speed bump of potentially monumental proportions.
For example: If someone is more community poly and they are dating someone who is more free-agent poly, there are likely to be some significant differences in desired relationship parameters. One partner who wants to be part of an extended family isn't likely to be happy at being kept in the background by someone who would rather maintain a "separate, but equal" expectation for their dating life. Unless this is brought out into the open, examined, and a mutually acceptable solution is negotiated, things are about to get bumpy! Personally, I would rather have expectations to live up to, rather than down to, but I'd like to know what I'm shooting for as well!
Another option for expectation management is to apply expectations only to oneself. This may look like knowing: who you want to be, what you want to give to others, and holding good solid boundaries on your emotions. It can be very challenging when there are differences in emotional intensity, for example, but as long as all concerned are sharing where they are at, the opportunities to put expectations onto someone else are minimal. This has been one that I've fallen down on in the past, and keep on my radar screen regularly as a skill that isn't automatic for me.
However you choose to handle expectation management, do handle it! This isn't one of those things that is just going to go away if you fail to recognize it, and it is something that can have deep and lasting impact on your relationships.