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This is a lovely post and I totally agree with you.
Personally I think one has to experience both loneliness and active physical friendship to be able to understand and appreciate life more as this would make a person decide what part is best for himself/herself.
Loneliness could lead to depression if the reasons leading to that point are unhealthy, but like you said it's important for a person to understand that it's more of a matter of decision than of necessity.
If I decide to be lonely, I know its best for me and that would help me grow in my personal life. However this can change at any time.
I also believe that we should learn to respect other people's decisions. In other words, if a person chooses to be alone, rather than get angry at the person, we should be understanding and respect such persons' decisions.