You are most "comfortable" with your own Sign and the other two in your Element (listed on next page). These Signs are most "similar" in that they share several traits and strategies for living. Friendships are easily made and maintained. These matches are "easy" - but not as "interesting" or "exciting" as the less similar Signs in the next paragraph.
You are also very "compatible" with any Sign in the Element compatible with your own Element. FIRE is best with AIR and EARTH is best with WATER. See
"What Are Compatible Signs?"
You're NOT very "comfortable" with any Sign in an incompatible Element - FIRE with EARTH, FIRE with WATER, AIR with EARTH, or AIR with WATER. See
"What Are Difficult Signs?"