This is a challenging and deep question.
On the one hand - day to day ups and downs are inevitable in any job and developing a certain degree of resilience to those is vital in any career.
On the other - leaving things until levels of stress, burnout or frank depression regarding a career that is not feeling "right" often results in a spiral downwards and at times this even precludes seeking career guidance. Why? Because the process of undergoing career guidance really effectively is one where a person needs to be in the right frame of mind - namely - relaxed, open minded and creative with time and energy to put to it. Rather too often we see professional people who are worn out and quite down about their career situation. In these cases we need to do some work with the individual to ensure they are not just wanting and needing career support but that they are ready and able to engage with it.
It is my view that our workbook is almost a diagnostic tool for depression in that when a person is suffering low mood - they find it almost impossible to complete it. This is because there are searching questions within it that require some deep mulling and if a person is struggling merely to function day to day then adding what seems like just one more stress is not sensible.
This is why timing for career guidance is far more important than people may at first realise. Yes of course an unsatisfactory career situation needs addressing but if you are not in the frame of mind most likely to help you address this - then joining our programmes are in short - a waste of money.
To try to help combat this need for "pre - career guidance" warm up - I wrote the ebook "easy career change good career choice". It covers a range of things to think about way way before getting to the career guidance stage. It seems logical if one is going to spend time and money investing in ones career to be well prepared for this rather than lurching into it without much thought other than "I am a doctor get me out of here".
So the answer to the question I think has to be this. If you have career doubts or feelings of mismatch or a sense that you are not on a pathway that is sustainable or attractive - the sooner you start to address this the better. You may discover ( as a fair proportion do) that you ARE in fact in a good career path but you are not handling your career or planning it ahead as well as you could be. Conversely you may discover that there are some fundamental areas of dissonance between who you are or would aspire to be and what the career path you are on can bring. Either way - the discovery process will aid things along. In short - I would say don't leave any feelings of career disappointment, drift, dissatisfaction, plateau or mismatch as they generally don't get better. They need to be acknowledged, flushed out in full and addressed in a sensitive, realistic, structured yet creative way.