Developing writers often achieve their initial successes by working with small, independent publishing companies. There are countless stories of songs that went on to become huge hits after being rejected by virtually every record label. The single stiffed and it was an additional five years and 200 rejections before the song became a top 5 country single for John Berry. Apparently not, but each rejection felt like it was sending the message that I wasn't good enough and would never be successful. As songwriters, we're regularly called upon to bear our souls, while maintaining the skin thickness of an armadillo.
Timing is another critical factor.
It won't matter how perfect your song is for Faith Hill if Faith just completed recording her album. It'll be at least an additional nine months, or even a year, before her record label and producer are seriously looking for songs. Once the demo goes into the mail there are at least a thousand factors that are out of our control. Keep plugging away. Hone your skills until you can consistently write excellent songs - and, occasionally, exceptional ones.