1. You choose the wrong goal.
On the surface, it seems like the goal of anxiety management should be to feel less anxiety. However, if your basic wiring is to react to novel and challenging situations by feeling anxious, then that's what it is.
Feeling anxiety isn't particularly dangerous. Most problems related to anxiety only occur when seeking to avoid anxiety impacts your decision making—for instance, if you have a concern but don't bring it up because you're worried about how you'll be evaluated if you do, or if a tendency to avoid situations in which you feel uncertain causes you to procrastinate.
A better aim is for anxiety to enhance your decision making rather than impair it. (More on this below.)
2. You lack accurate meta-awareness of how anxiety impacts your decision making.
Becoming an expert at managing your anxiety, involves a very sophisticated type of self-awareness. Specifically, you need to be self-aware of how anxiety tends to impact how you view situations and the choices you make. For instance, if you're rigid about needing to have all your plans nailed down far in advance, you might find that you will stick with a worse plan rather than walk through a different door that unexpectedly opens.
As a specific example, imagine that you have a plan to buy a single family home as an investment property. A great deal on a duplex comes up, but because anything unexpected throws you for a loop, you rule out the better option. Alternatively, imagine that you make vacation plans and get unexpected bad weather but you persist with your outdoor activity rather than revising your plan.
Most people who are anxious tend to prefer sticking to the familiar and certain. However, anxious people differ in terms of whether they respond to anxiety by trying to control everything themselves, or whether they go in the opposite direction of handing all control over to other people because responsibility stresses them out. Likewise, although taking too long over decisions is the most common pattern, sometimes anxious people rush into decisions or put off researching their options because looking at options is so stress-inducing. When you know how anxiety typically impacts your thinking, you can keep an eye out for those biases and correct for them (I personally make corrections to my own thinking at least several times a week.)
3. You try to do everything yourself.
Anxious people often believe the only way to avoid catastrophes is to do everything themselves or at least stay on top of every aspect of a project. Not only is this exhausting, but there can be other downsides, too. If you always take care of everything, it's easy for other people to come to expect this. Training other people to take responsibility is a more sustainable approach, and frees you up to concentrate on the parts of tasks and projects that are best done by you.
4. You push for a resolution when waiting for a situation to play out would be better.
Since anxious people dislike uncertainty, they typically want any uncertain situations resolved as quickly as possible. Sure, there are times when getting an issue resolved and squared away quickly is preferable. However, there are also scenarios in which it's better to wait to see how a situation evolves. You can potentially save yourself unnecessary work by doing this, and the resolution you get if you're prepared to wait for it might be better.
Likewise, if you always rush to resolve unexpected situations straight away, you might find you spend all day putting out fires when you have more important priorities for that day.
5. You try to reduce your anxiety to zero.
Feeling a degree of anxiety, especially about big life decisions or when you're trying new things, isn't a big deal. It's okay to find it hard to get to sleep, have a few weird dreams, feel physical anxiety symptoms, or find it hard to concentrate when you've got important things going on in your life.
Anxiety strategies should help you reduce your anxiety to the point where you can think clearly and keep putting one foot in front of the other towards your goals. Try judging the success of your strategies based on whether they help you get a clear perspective on the situation, rather than whether you're still feeling a bit internally churned up from your anxiety.