So, I recently got diagnosed with autism. Because it is a spectrum that is more like a color wheel and less a straight line, we can all have different levels of each characteristic. We have all kinds of cognitive abilities at every level. Some of us want to be social but feel like aliens because we struggle to understand others' reactions to social interactions. I learned through observations and trial and error. We feel empathy, but we may not interpret the feelings the same as the person feeling them would.
So, anyway, essentially, the answer is observations. I literally took notes and did "social experiments" as I was growing up. I wasn't particularly aware of what was "mean" or "nice" and would cause the children in elementary school to become angry with each other over hearsay. The kids would never seem to ask the person they were pitted against and I would have notebooks filled with notes. People seemed to get arbitrarily angry with each other but would never tell each other why. I learned about ethics growing up and learned to ask questions that would give me more answers from their body language, time it took to answer, and gauge their reactions from either myself or a male to a male or female, etc., in high school.
Throw some trauma in there for physical, emotional, sexual abuse throughout my adolescent life and continued (up until 2yrs ago, I'm better now) on to adulthood.
Life is a series of learning experiences. If you ask enough, you get answers from their poor reactions or from their actual answers. You learn how to ask. I always ask people that are angry with me, what have I done to upset them and what could I change to avoid this in the future. When I was younger, I would trigger some issue they have and would cause them to believe I was attacking them. This causes them to activate their sympathetic nervous system and see everything as a threat.
I'm getting off topic.
Read! Research the specific hurdles that are causing you to feel held back. You know, better than any of us, what specific issues are arising. If need be, write them down. Write them down in any way you'd like. If you have the opportunity, ask people you are having problems syncing up with about what they feel the problem is. If you struggle to understand others, ask them. If they're upset with you anyway, what could it hurt (assuming this isn't an abusive/ dangerous situation, in which case please avoid these people)? Most people are taken off guard and will realize that this is a struggle and will want to help you. If how you ask angers them, ask them what you said that made them upset. If you want to move up to becoming more pleasurable, then study people that are very sociable. My friends believe that I am very sociable, but it takes a lot of energy for me because I am constantly having to go through my mental library of what certain reactions and words may mean coming from people of certain genders, ethnicities, and where they grew up (if known). You can most certainly learn from those around you as well. Learn from their successes. Learn from their mishaps. Learn by breaking down what happened into honest and realistic actions or inactions.
There is a pattern to most everything. Luckily, I excel at finding patterns (most humans are naturally good at it, they just may not notice they do it) and I can use this skill to understand the humans around me. The more information you have on human nature, whether from a posteriori, a priori, or reading/watching videos, the easier it will be to know what reactions certain people may want or need from you.
Most importantly, if you feel insecure because of some internalized past failed interactions, take a step back and ask yourself why you feel this way. Your feelings are valid, should be felt, and released in healthy ways (exercise, meditation, yoga, etc), but they should also be analysed. Do you think that the level of emotion you felt makes sense for that interaction? If not, have there been other times that you felt more emotional than need be? If so, then you may have some underlying feelings that you have not dealt with and need to face in order to progress. Whether it be with a therapist, a trusted friend, or on your own (by typing it out, writing it out, saying it outloud to a recording app or device), it needs to be let out and understood.
Asking questions is the first step to understanding and therefore mastering. There is no losing, just winning and learning, in life (taken from Nelson Mandela). This means that as long as you take time to understand what happened and implement plans to adjust, you are only ever learning, or otherwise winning. *internet hugs*
Sorry, I got carried away. I struggle to keep things concise. I hope this helps.
If I may, where did you learn these things? I am reading a book on trauma and some people with a history of trauma and abuse can lose the ability to synchronize with others and may have autistic qualities. I have a history of trauma. So, there may be some overlapping qualities. I would love to pick your brain or research. :]