Darts is not a panic game
Darts is an enjoyable game and should be looked at in a light-hearted manner. You are allowed to feel joy and disappointment but don't let emotion disturb your physical state too much during the game as having your heart pumping wildly only makes it more difficult to be accurate. Before throwing each set of darts a well-executed sigh or breathing out will momentarily relax you and make your hand and aim steadier. As with any sport or physical activity regular breathing is important even if you momentarily stop while the dart is thrown. Make sure your darts are the best weight for your throwing style. Experiment if you need to, and can afford it. Make sure that the dart shaft that holds the flights is the best length for your style of throwing. Even though many will argue that it is important to stand with both feet on the throwing line parallel to the boards face, it is very important to find a reproducible way and place to stand. The one that is most comfortable is likely the best as you will gravitate to this naturally.
If the dart does not feel comfortable in your hand then try a longer or shorter shaft or a different style of dart (thinner, thicker, rougher, smoother) until the balance or feel seems good. Following through tends to improve your performance although this is not "written in stone ". If you overextend during your follow-through you may feel pain in the inside elbow. Reduce your follow through and release the dart slightly earlier. If you need to straighten out darts that "lob" toward the board then instead of throwing the dart harder and destroying your aim throw the dart a little faster. This way extra force is not exerted by your hand but just by the speed of your arm and the release of the dart in the same trajectory. Attempt to get your darts to enter the board face at right angles but don't give up throwing because they aren't. This would be ideal as they then present little blocking of your view of the board for the remainder of your darts and are in the least way preventing the following darts from entering the board. If you can wear the same shoes that are comfortable and yet somewhat supportive so that the way you stand and feel is the same each time. Wear unrestrictive clothing especially the shirt/blouse or t-shirt. Nothing should interfere with arm and hand movement when throwing. Look at the target (the spot you want to hit) and only throw when you are focused on the spot even if you have to relax again and refocus later before throwing .
Darts is not a PANIC game.