Personally, I don't try to make lyric fit a melody, I make the melody fit the lyric. When I first started writing, I did what I suppose everyone does initially, the follow-the-bouncing-ball approach...even to the point of counting syllables. Early on in my career, I was fortunate enough to become friends with Dave Loggins (whom I learned so incredibly much from) and he was the guy who turned me onto the idea that the most important thing was what you were trying to say...therefore, the melody should conform to your lyric & not the other way around. Completely changed my way of writing and opened up so many more musical possibilities to me.

If you have a very critical lyrical thought/line, there's usually a way to make it work...you just have to be creative with phrasing and be flexible with the melody.

http://www.rogerbrownsongs.com
http://www.nashvillesongwriters.com/roger-brown