Let me argue both sides of the it, with the thoughts that have flooded my brain since the past few weeks.
Reaching the planned destination is in itself a feeling of achievement, but there is a huge possibility, that the life which lies ahead of the destination doesn't give you the happiness you were expecting from it. This very moment when we realize that we are not happy, we tend to think that planning never works out and we should never work according to plan, and its better to live life unplanned. But we have got this wrong friends. Living a life unplanned is not going to give you happiness, but an easy way out devoid of happiness or any accomplishments, it is a definite way to escape, but will keep your fundamental question unanswered that is "What is the purpose of your life". You should realize the moments, the feeling of achieving the planned destination was phenomenal, and that made you happy, but the thing which needs to be fixed or worked for the next plan is the selection of destination. This is the actual problem for me and a lot of others, we don't know what we actually want. I do things, I plan them, I achieve them, but then it turns out I didn't actually want it. Does it happen to you?
I planned to get a good paid job, to be specific, concretely wanted one, in which I get above 12 l.p.a.. I did achieved this, that made me happy, but now I don't know if I actually wanted this. Adding to it, I don't know what is it that is wrong with the job and what changes do I want from my next destination. But I am trying to figure out what I want, I am confused, but I know about it. I am working on finding it out, and want everyone to do so. The sooner we know about our destination, the more time we get to live the life we planned for ourselves in our head. The life lived there on would be better.
Its really frustrates the hell out of your brains, when you reach the destination you planned and then you are finding the next destination instead of living the life you expected to be awesome. The thoughts like the companies use you like a robot, you are not going to get anything out of it, why I am I wasting my time here, is it better to work for a startup, the life is so monotonous here, why have the other people not left their jobs yet, what should I do next?, where should I get something I want, and many more have been playing with my brain since few days. Somehow I still work for around 8-9 hours, do productive work, remain happy and enjoy my time, with these thoughts in my backend. That all happens because I keep saying to myself, that Relax Kid, you will figure it out soon. If it wouldn't have been in my mind, I would have surely broken a lot of things, or would have injured myself.
So the real problem that we face today, is we don't know what we actually want, what are we after and what is going to give us happiness! Face it, solve it and then move towards it :)
P.S. I am generalizing my observations to be true for all, but that's how I feel about it.