I think David's first mistake could be called drifting. It was spring, and in the spring kings went to war. It was what they did. In fact, the primary reason the Israelites wanted a king was so they'd have someone to to lead them in battle (cf. 1 Samuel 8:19-20). This is what David had done every year, but, for some reason, this year he just didn't want to. He said, "You guys go on without me." He seems bored, listless. The text says, "One evening David got up from his bed." That's what I'm talking about. What's he doing in bed in the evening?
As far as we can tell, David's about 50 years old now. He's not a feeble old geezer. But he's not a young boy anymore, either. His eyes are probably starting to dim a little. His hairline may be receding; his waistline is probably expanding. He's had them some extra fiber to the royal diet. He's got a treadmill in his office. Grandmothers come up to him now and say, "When I was a teenager I thought you were so dreamy!"
He was always so passionate -- about everything! But he doesn't feel that passion anymore about anything. He's restless. He's drifting.
There may be nothing as dangerous as a passionate man who has lost his passion. He is a danger to himself and to those around him.
The bizarre thing is that he used to talk to God about everything. Good or bad, he'd just bring it right to God. But now...he's not even talking to God about it. Maybe he doesn't know what to say. When God finally confronts David about the whole episode (through the prophet Nathan), he says, "I made you king. I protected you from Saul. I gave you this kingdom, and if all that hadn't been enough -- if you'd wanted more -- I would have given you more. Why didn't you come and talk to me?"
The best thing you can do when you're bored is talk to God about it. But a lot of us are afraid to do that. The reason I have a hard time with this is because of what used to happen when I was a kid. I would tell my mom I was bored, and she would decide that this was a good time for me to clean the bathrooms. Or mop the kitchen. Sometimes I think that if I tell God I'm bored he'll send me on some horrible errand that I'll hate and will be tremendously painful.
Do I really trust that God is good and has my best interests at heart?
That's kind of what it comes down to, isn't it? If I do, I'll be more apt to bring all my thoughts and feelings to him. If not, I'll be more likely to allow myself to just drift. And that's where the trouble really gets started.