I'm kind of a type "A" person. OK, I'm a VERY type "A" person. I even cook by setting things up ahead of time. I'm definitely more in the "Plan and Prepare" camp than the "Just Do It" camp.
But I do realize that there are times when you just can't stop and prepare. Sure, it would be great to know that server is going to melt down just now, but it happened and you have to deal with it. Now is not the time to open the plastic on that "Troubleshooting SQL Server" DVD course you bought! You just have to dive in and get the thing fixed.
Hopefully you're not operating like that all the time. If you are, you probably need to get some help with your systems, at least temporarily, until you can get them stabilized.
So which is it? Should you be like me, a type "A" who has to have everything planned out, or a reactionary agent, fixing things as they happen? How about - Both!
I think you should aim to plan and prepare as much as you can. Your life will be more stress-free, and you'll be happier in your job. But you can't lose your head when things go wrong and demand time to plan and prepare. You just have to jump in there and fix the problem.
But I think there's a happy medium in there somewhere. I ten to plan and prepare for the times I have to "just do it". I have my scripts ready for things like backups, DBCC repairs, restores, web site links for "how to" articles and so on. I have those right by my desk so that I don't have to panic when panic hits. So in effect, I'm doing both - I'm planning to just do it.