Some writers hold back a little in a manuscript. They don't want to risk leaving their well of ideas empty for their next project. To me, that's like the Indianapolis Colts holding back when they were undefeated at 14 and 0. Their front office didn't want to risk injury because they wanted to guarantee that the Colts could go into the playoffs healthy. So what happens? Dwight Freeney gets injured anyway in the playoffs; in practice, Reggie Wayne worsens the right knee injury that has plagued him throughout the season; and, despite all of Peyton Manning's determination and preparation, the Colts lose dramatically to the Saints in the Super Bowl. Why? The New Orleans Saints never held back. They left everything on the field in every game all season and post season, while they were undefeated, and even when they started losing. They still played with heart. The Colts management played it safe and the players lost heart. Winning - and writing - is all about heart.
Never hold back when you're writing. Put everything you've got into every manuscript you write. More ideas will come for your next project, ideas better suited for that project, but if you shortchange what you're writing now, chances are you (and your current manuscript) will lose heart, and won't be able to go the distance. You have to be willing to risk it all, and put it all on the page. The Indianapolis front office wasn't willing to take risks - New Orleans risked it all on tricky plays like an unexpected onside kick, and today the people of New Orleans are starting their Mardi Gras celebration early with their Saints and the Lombardi trophy in hand. The Colts are going home, having fallen short. Don't let your manuscript fall short because you held something back.