I think this involves many factors. Some people do maintain their success for many years while others despite their best efforts can't do it. Also if a famous person has other problems in their life those seem to become worse after their fame is achieved.
I think a person has more to look forward to in their life if they have a dream, no matter what it might be. Sometimes it seems I've chosen a difficult goal, but I think that's in part because I enjoy having something challenging me.
The main thing is to enjoy the present moment. Although I know this isn't easy to attain. While on the journey it's natural to feel frustration when things don't go the way you would like. Some give up on their dream and maybe switch to something else. I don't think there is anything wrong with trying something else, but I think people benefit from having something to look forward to in the way of achievements. One shouldn't shy away because things get difficult. The best thing to do is focus on making small steps of progress.
Some of the things I find enjoyable about the journey are:
1. Seeing improvements in my own writing.
2. I've made some great friends along the way in writing groups and/or critique partners.
3. My few successes in being published and a contest.
4. Finishing a novel ( a couple of times)
5. Everything I've learned about writing and publishing.
So today, think of what you find enjoyable along your journey.