Avoidant attachment develops when caregiving is emotionally distant and strict. These parents are often emotionally misattuned to their children. They do not tolerate emotional expression and expect their child to be independent and tough. When their child is reaching out for support, reassurance or affection, they tend to pull back.
This leads the child to learn that they cannot or will not get support, affection from their parents, leading these children to develop beliefs that emotionally intimate relationships are unnecessary and will not or should not meet their needs, just as their caregivers did not meet their emotional needs.
In adulthood these individuals tend to see themselves as strong, independent, and emotionally self-sufficient. They tend to be confident with a positive self-image and good self-esteem, and they don’t believe they need to be in a romantic relationship to feel complete.
Their working model of intimate relationships is that they are not necessary, although they might be very sociable, fun to be around with many friends and/or sexual partners, they do not tend to get too close to anyone.
For avoidantly attached adults, they are not necessarily lonely or loners, although they can be. They will allow you to be around them, but not get too close. If things seem to be getting serious or too intimate they tend to close off or find a reason to end the relationship.
Source: The Attachment Project