All of a sudden, my MacBook Pro is running very slow?!?

I have had my MacBook Pro for a about a year and a half and have had NO problems with it. A few weeks ago, my MacBook has become very slow, to the point where I have to restart the computer. Most of the time the dreaded beach ball appears and my MacBook just freezes. This occurs with the simpilest tasks such as opening Safari.

This is becoming very frustrating and I am losing my patience, I am hoping it is something that I can fix on my own to avoid going into Apple.

PLEASE HELP!