I'm 40, have been working in technology for close to 20 years, and have had the great fortune to have stayed employed for most of those years, but for the entirety of this I've considered myself "underemployed". I've woken up each day thinking "boy I could be doing so much more if only I wasn't limited by [ ROLE | COMPANY | GEOGRAPHY | BOSS | ETC ]. Don't get me wrong--I feel grateful that tech is one of those careers where you at least have a chance to improve where you are, but these opportunities are still few, far between, and you have to pound the pavement to find them. You do need to plan and you need to ask the right questions of yourself. I like this article because it provides some structure for your plan and helps you to think about the good questions to ask yourself.
My entire professional life I've never had trouble finding, often very fulfilling work with great compensation. But I always had a niggling feeling that I could be doing more. Planning helped me to realize that my true goal is to make an impact (even a small one) on millions of people, so now I'm taking the steps to make that happen.
Also, to paraphrase Eisenhower, it's often not the plans which are most beneficial but there mere act of planning. My plans usually turn to rubbish, but the process of planning helps me to center and crystalize my thinking.