Viswanathan Anand vs Magnus Carlsen Linares-Moralia 2007
Did you ever capture a piece for an even exchange only to realize that you set yourself up with a lost position. Here's an example of why it's important to visualize the position before you make your move. Young GM Magnus Carlsen actually took with equality only to realize that he allowed a pawn to become passed and it ended his game several moves later. The theory here is tension. Many times the person that opts to relieve the tension pays dearly for it.