Song writers often reach a point where they feel that their songs are boring or that they lack something special. Often times, simply repairing a single moment in a tune can dramatically change the way a song sounds. Simple changes like altering chord progressions or the length of a phrase can create quite a difference. Also, experimenting with different keys and tempos can change the emotional aspect of a song.
Some great tips:
Do Your Songs Bore Even You? 10 Ways To Write Better Music