It may be unrealistic to think that a friend will be able to be supportive of you all of the time. However, the personal relationship and interaction you have to someone crosses that line between acquaintance and friend. We can think of a friend as someone whose personality or hobbies we enjoy when we're around them. When you spend time with a friend, you build a trust that you can say or do almost anything, and although your friend might think you are weird sometimes, they will continue to think highly of you and not be judgmental. Think about it.
Nobody is perfect.
But, it is the exploration of interest and the curiosity of life that, when shared with a friend, is an interaction that shows how friendship is important in our lives. It is in this regard that we can look at a friend as someone whom we trust and not feel judged. Friendship slowly builds over the years. It is this establishment of becoming aware of your friend's personality on a deeper level that establishes a level of comfortableness in your friendship. Upon this assurance, a friendship can withstand any disagreement or misunderstanding through communication of hurt feelings.