You should do exactly as you want. If you are content, don’t worry about the expectations of others.

You don’t need the approval of your friend and you certainly don’t need to change for a single person. However, yea I’d say this social isolation measure is extreme which you should consider going back to counseling for.

Is this the same "friend" you posted about in the past, who said you failed to meet her friendship needs and called you a narcissist? If so, I think you need a different friend. If you have a friend who spends time telling you that you are bad at things (unless it is baking a chocolate cake or quilting) and that you have mental disorders, I don't think you should hang on to them as friends.

As to overreacting, yes I think if you isolate yourself further because someone said you don't have "relationship skills" you are not reacting appropriately. I can't say what your "skills" in this area might be. Maybe you don't attend well to the emotional needs of others but maybe your "friend" is overly emotionally needy. I've dealt with people like that before and if you do not spend much of your time focused on their life, day-to-day stuff, their wants, their frustrations and everything else about them, they take it as you are not being a good friend.

If you are concerned about whether you have adequate relationship skills then perhaps this is something to discuss with a therapist. Before that you could sit down and write down what you think a "good relationship" involves. This would be with anyone although more intense relationships will by their nature involve more things. To me, an important part in any relationship is equality. You get things from the other person and you give back to that person at roughly the same level.

This includes the simplest relationships, like one between you and your hairdresser. You follow protocol, showing respect by making an appointment if that is what she expects. You show up, you exchange pleasantries with her and chat amicably while she does your hair. When she is done, you pay her for her service and bid her farewell. Obviously, a friendship requires different interchanges but the same principles, you give them attention, listen to what they say and respond warmly. You offer advice when they elicit it, sympathy when they are sad, understanding when they are upset/angry. In exchange, they give you the same kind of attention.

Spend some time figuring out whether you actually fail to do "your share" in relationships you may be in. Assess whether you are actually doing any harm to others with any missteps you might make in a relationship. There are times in any relationship when things are not exactly right but that doesn't make it harmful to the other member. If you attack the other emotionally, in cruel, hateful ways when things are going poorly, then yes that is harmful. If you constantly and consistently refuse to listen to their woes, their highs, their lows and seek only to focus on YOUR needs, then yes, your skills need improving but I doubt you are conducting yourself in that manner.

Not to bring politics into this but look at Trumps interactions with people. His consistent treatment of people who don't praise and adore him or at least pretend to do so. This is someone truly, woefully lacking in relationship skills. If you conduct yourself like he does, then run, don't walk to a therapist and hope for help. If, on the other hand, you sometimes engage in relationships that take a negative turn or are not always equitable, spend time working on ways to change that rather than isolating yourself from others even further.

As it is, aging brings with it more isolation and retirement increases it further. While introverts value "alone time" and have less need for social interactions than extroverts, isolation is different. Isolation takes away support systems, it promotes depression in the elderly, it can increase disease processes. Look for ways to increase rather than decrease your social/emotional supports. Stay involved with family events, just avoid getting "cornered" by the members who are all about politics/religion or other uncomfortable subjects. Look for ways to find more people who share some interest with you, find places you can offer something, volunteer, whatever will expand your social options while still allowing you control over "obligations".

I am an extrovert, but recently I have quit being as social as I have been all my life. I am not worried about it. I am comfortable with it. If you are comfortable with it, don't worry about it.