I've also seen a lot of career mistakes over the years. Here are a few, and how you can avoid them.
Outdated thinking about career security
While there is much you can do to protect and maximize your own career-ability, times have changed and old notions of job security need an overhaul. Today, you need to think in terms of "gig' (even if you have a full-time job) and constantly stay on your "career/change-ready toes."
Complacency
If you've been coasting for too long now, two words for you: wake up! Career complacency is bad for your health, professionally and personally. Stagnation puts your career at risk.
You need not have aspirations for a huge vertical career trajectory, but it's always a good idea to develop yourself in some way, shape or form. Get a goal; learn a new skill or three; connect and get out there. Do some or all of this and you'll be safer, happier and healthier too.
Risk aversion
A good measure of prudence can be wise, but not too much. Insisting on certainty at the expense of taking some healthy risks can derail your career over the longer haul. Over-investing in the illusion of safety can actually can hold you back from taking stretch assignments and new opportunities to grow and build upon your career experience.
Nothing is guaranteed and indeed sometimes a decision may not work out for the better. But this need not derail your entire career.
Networking blues
I talk to a lot of people who have an aversion to networking. Sound like you? If it feels "icky," chances are you may not have learned how to connect authentically, purposefully and reciprocally.
Avoid networking at your own peril. Get more comfortable by learning how to connect authentically, and since this is a skill for life make it high priority and not just for when you need a job. Successful careerists know healthy networking is a year-round, career-long necessity.
Blind to your own super powers and accomplishments
Most people are so busy getting stuff they lose sight of the miracles they perform every day in large and small part. They fail to recognize their own strengths, abilities and talents. As a result, when it comes time to speak to their worth and value, they sometimes sell themselves short — even to themselves.
Some people are simply modest, but when it comes to careers it can be at their detriment and they need to get better at conveying their value. You need to be your own brand marketing officer! Make this the year you learn and/or rediscover your unique strengths, abilities, success stories and how to convey all this with confidence without feeling like a braggart.
Stuck in limiting beliefs of shame
Sometimes people feel embarrassed about being laid off and/or not yet having landed a new job. This feeling of shame holds them back from reaching out (network, recruiters, etc.) and leaning into their job search.
Stop that train of thought! This is a self-limiting belief that does nothing good. Lay-offs happen. Companies change. And even if you were let go because of poor fit, so what? It happens to many incredibly successful people. Move on. Your self-limiting thoughts can become your biggest obstacle.
Procrastination
You know better, and yet, you're still not taking action. There are lots of reasons why people procrastinate when they want or need to make a career change: they are overwhelmed; uncertain how to navigate the way forward; feel daunted; lack confidence, and more.
Staying still and doing nothing will only dig you deeper into the hole of self-doubt and inertia. The most important steps to take are the first ones, and tiny ones work just fine.