While it often seems like we are all alone, the truth is, we are never alone. It only seems like we are.
In one sense, we are alone, in our own heads. We have a theory of mind that allows us to posit that other people have thoughts going on in their heads in much the same way we have thoughts going on in ours, but that is only a theory. We are stuck in our own heads. So, in that sense, we are alone all the time.
However, we are also biologically related to all life on the planet and chemically made up of the same stuff that makes up the universe. It's mind blowing when you think about it.
If we focus on just the humans and our connection to them, there are 7+ billion of us alive at the moment. We are all similar yet different. The key is to understand and accept the similarities and differences at the same time. When you can do that you get that each human is real, not just an abstract idea of a person, but a real person with a real life and real problems and real loves and a real job you know nothing about. The problem we have is that when we interact with other humans, we see and judge the interaction through our own lens of experience. The problem is that this provides us with a distorted view of the interaction. The other person or persons have their own lenses they are viewing things and judging things by and their own distortions.
What helps improve interpersonal interactions is to accept that your view is limited and inaccurate and seek to grasp the inherent realness of the other person’s experience. This requires you to get out of your head and to consider the other person as a person and that requires compassion (despite what horrid thing they may have done). The beauty of doing this is that the act of consider people compassionately takes you out of your head, where you are stuck, and connects you emotionally to other people so that you aren't alone anymore.
This aspect of compassion is the reason every major philosopher and teacher and religion teaches compassion in some form. It's incredibly powerful and helps eliminate that feeling of aloneness that is at the heart of most of our existential angst.
As to the question about ethical principles - all of our principles are a product of learning and experience and shared community. So even if you think your principles are yours alone, they aren't. They are a rather arbitrary mix of your own thoughts and what you have learned from and with others. Ethics is a communal activity. You can't do ethics or be moral in isolation. You can only be moral in relationship to other people. So no, in that sense, you don't stand alone even when you think you are.
What do you do to combat the feeling of being alone in the universe?