Don't be emotionally cut off.

If you have spent a considerable amount of time with someone and have known someone longer than to merely consider them an acquaintance, then open yourself up to the possibility of connecting on an emotional level.

Do NOT keep yourself emotionally disconnected from people, especially the ones you would like to call your friends.  If you feel like you are emotionally disconnected with others, then you may need to take a look at yourself.  You may be the subject of your own emotional disengagement.  You might harden yourself and close yourself to the broad spectrum of emotions that humans experience: joy, pain, excitement, frustration, anger, anxiety, love, hate, etc.  You might do this to try to keep yourself constant, consistent, stable feeling.  It probably starts with hiding the expression of these feelings though you still feel them on a real level.  Use caution when filtering the expression of your emotions though because if you do it too much then you run the risk of becoming hard and actually feeling less.  Eventually you will get to the point where others realize your hardness and emotional closure and people will become distant to you.  In order to avoid this, it is important to have a select few people in your life that you are emotionally connected to.

Being vulnerable and/or sharing your feelings with a level of depth to someone isn't always easy, but it is important.  It isn't simple, but it can be simply put:  Be open with your friends...or you might lose them as a true and lasting friend.

Good luck.