The person who is there for you regardless. The one who you can be open with, share your fears, anxieties, and frustrations, and with whom you can admit your failures—the one who will question yet not judge. For them, you are who you are, and they strangely welcome your imperfections and peculiarities.
It is the person who will tell you where you may want to consider an alternate perspective or that this may not be your best idea yet. The one who will advise you from making a fatal mistake, yet leave you to choose, and if you do, support you completely.
When you abandon them for a while and come back, they are the ones who will likely move forward as if there was never a break. Why? They know your flaws better than you, and it was never you abandoning them, but you lost.
We all need one, only one.