Before you begin with an apnea discipline such as statics, dynamics or depth, you have to prepare yourself. Many divers practice yoga, stretching or mental exercises. No matter what method you choose, try to set it up as a ritual before a dive.
An important aspect is that you loosen the breathing muscles and warm up. In very deep inhalation the lung tissue and surrounding muscles are stretched. This will be easier the better you prepare yourself. During deep dive, the chest is strongly contracted. This also works much easier after a warm-up phase.
As a part of the preparation, you should go through your dive in your head. For example, count your breath before dive. Count the fin strokes you need to reach a depth. Count the seconds before the diaphragm contracts in statics. Count the seconds you need for a 25 or 50 meter track. The more routine you get, the safer and more relaxed you will dive.