You focused your energy, you sacrificed in other areas of your life so you could achieve your goal. After time (and perhaps some struggle) you have made it and you have celebrated your success. Now what?
After the victory dance is over after a big goal is achieved it's not uncommon to feel like something's missing. It's not that the goal had no meaning - it was a huge deal that you went for it and accomplished it - your issue is that the purpose the goal gave you is gone.
Some people drift for a while after they have accomplished something big that they set out to do. It might partly be because they have expended energy and need to refuel. But there's another factor as well. Once you have fulfilled a need it no longer motivates. If you set out to have $100,000 in the bank, once it's there its power to move you is gone.
Purpose is what keeps people going. Imagine achieving your life goals by age 35 and realizing that you have 50 or more years to go. The striving is what gives your life its excitement, its meaning. This doesn't mean that you have to resign yourself to being a stress monkey forever - it means that you need something to look forward to.
If you are drifting after accomplishing a goal, examine the things that you put aside for the goal's sake while you were working on it. Perhaps you now have an opportunity to add some balance to your life - the life cycle version of balance rather than the daily or weekly version. Perhaps you've got a secret project that has received no attention that can now receive some of your energy. If nothing in particular is pulling you, perhaps it's because you have kept these other dreams and aspirations on the back burner for so long that they need a little nudging to step forward.
We are faced with many times of transition in our lives - some of which we choose and some that are imposed upon us by the order of things. The time immediately following the achievement of big goals is one of those transition times. If you're concerned about getting stuck in that drifting mode, this is one of the times where a coach can be helpful to you. They can provide tools to help you discover the next mountain you want to climb.