This is the point where the argument went off, I believe. People only listen to what they want to listen, and generally they care less, or won’t bother to care at all, if the topic is not somehow related with themselves.
So no, the lack of understanding you by other people is usually not caused by the lack of skills to explain yourself, but more often caused by human nature.
Although I still believe that self-understanding and communication are fundaments, other people are also important factor in this equation.
I wrote complementary points in this comment: https://news.ycombinator.com/item?id=34497083
> So it’s your task to make others understand you
There is another task that is just as important. You need to find people who are capable of understanding you. It may sound like a cart/horse issue where you need to understand enough about yourself to find people who are receptive. That my be true to a degree. But no amount of self-understanding is going to change how people respond to you if who you are is not comprehensible to those people.
As an example, imagine you are a straight man with many close friends who have known you for a long time. And at some point, you begin to grapple with the idea that you're not straight, but maybe bisexual. It is possible that some of your old straight friends will have the capacity to listen and understand and respond in ways that make you feel known. But it's not necessarily likely. And if those are the only people you are close to, no amount of self-knowledge is going to change their capacity to make you feel seen and heard.
You're gonna need some new friends.
1. Understand others, therefore can describe them in a way suited to their way of thinking. This is probably controversial assumption but I believe people are unconstrained, everyone can understand everything, it may just require more time. If you believe people are constrained, or just don't want to spend time on them—find people who are capable of understanding you right away. By being honest about yourself you will attract like-minded people. The process of "explaining yourself" obligates you to approach new people (not only your current closest) and explain them your existence. If you feel understood only by your closest friends, then you are not good at expressing yourself.
2. become less self-concerned. You no longer seek validation and significance—you are fine with being normal. You no longer need someone who will make you less lonely, someone who will fix your flaws. You no longer focus on yourself (you know this guy good enough), rather, you pay all the attention to others, you become emphatic, which connects with others, and thus you become less lonely.
3. You can honesty communicate your needs, fears, desires, emotions. They are part of you, and hence it's your responsibility to explain them to others. Don't expect people to read your mind. Don't run away using abstractions, give concrete examples. If you believe in small lies for a greater good, then you are not communicating yourself. If you consider breaking up with your SO, talk about it with him/her, not your friends. If your boss annoys you, tell him which actions annoys you. It requires a lot of courage therefore little people do so, but not doing it results in loneliness. You have a choice.
This is embarrassingly over-simplified. Maybe don't immediately turn every half-baked shower thought into a blog post and post it online.
Also, I would not be surprised if Nobel price ideas were invented under the shower. Actually it's the most likely that synthesis happens during the diffused mode of thinking, which happens under the relaxation like shower.
I don't claim my idea is worth Nobel price. I just explained in succinct (possibly over-simplified) way my experience of feeling misunderstood for most of my life and the solution that finally helped me.
I shared it to validate whether it's a solution to all causes of loneliness or just mine.
If "Loneliness is a measure of self-understanding", how can you measure it?