Stoic (English)
Learn how to be alone and satisfied. You know you were not borne to be fully alone because your ancestors would not have strived in a wild world without their working in groups.
However, you know that introverts have always existed. Lone people have always existed since the beginning. This is not a disease. Solitude is not a disease.
Learn from the past, but do not let it misguide you. What you see is a mere set of images which manipulate your feelings and brain chemistry. Do not be a slave of your memories. Live now.
What is the point in caring for what people think of you if they see you alone in a restaurant? People judge each other from a comfortable place, just like those who mock someone who is speaking in public. All they say, all their sneer is a show of fear - their fear of putting themselves in a difficult situation; they fear mockery and rejection. Do not crave the attention of people who don't cultivate good morals.
Learn how to admire things as they really are. Strip them bare and you'll see how shameful it should be for you to feel down because of a mixture of things that were put together and make you feel so. But actually it is not those things which make you feel this way, it is your judgements towards them - those things are particularly harmless if you analyse them detached from the form which is the source of your discontentment.
Do not judge. Observe. Accept. Change.