A friendship with an Aquarius is one that's built naturally and is likely to remain all your life. Aquarians are protective of the people they love, and as stubborn as they can sometimes be, they rarely get angry (via YourTango). While they can sometimes disappear into their own heads, for the most part they are among the most attentive listeners and caring people you can have close to you in your life. 

Your friendship is likely to grow over long, deep conversations. This is how this air sign comes to know, trust, and connect to you. And once they've counted you as a close friend, they will show up for you faithfully. As much as they care about the causes close to their hearts, they care about the people in their lives equally, and will protect, defend, support, and cheer for them with equal fervor. 

You can trust an Aquarius to keep whatever secrets you tell to them, and they are great at helping you analyze a situation or make a tough decision. All that time in their heads really does pay off.