Think of complacency in this way. You've just climbed and scaled a large mountain. Now you've reached the top. It feels pretty good, doesn't it? But, climbing the mountain is only half the battle. Unless you're wanting to stay up there, you are going to have to go back down at some point.
Despite gravity being in your favor at this point, you can't necessarily just slide down the other side of the mountain. There's work involved, and sometimes, it's even worse than you think. In some cases, the way back down can be more treacherous than the way up. Then, the momentum that gravity gives you may not be as much of a positive as you first thought.
Maybe you never make it back down. If you're not careful coming back down, a successful climb can then into a tragedy. At the very least, an overall failure is always a possibility.
Once you've enjoyed a major success, it’s very enticing to rest and reap the rewards of your achievement. Being content is OK for a moment and taking a vacation is fine. But, you have to get back to work at some point.
Sure, you might build a big garden on the mountaintop. You can sit back and enjoy it for a little bit. Then, you can even hire somebody to care for it for awhile. But if you're not careful, the weeds can take over and the beautiful flowers can wilt.
Sure, you may get to the top of a great mountain, build something beautiful and want to just sit back and admire your handiwork. But, if you go down the mountain, you never know what awaits you on the other side. If you keep moving, you may find even greener pastures. Possibly, there could be greater mountains to climb. And there usually are.
If you keep moving and stay alert, the reaches of your success can be unlimited. Let your success be not an end, but the beginning of something even greater. Always let your momentum carry you forward.