"I just can't seem to calm down."
Anxiety, by definition, is worry or uncertainty about something happening in the future (near or far). Anxiety can come with many physical symptoms such as rapid heartbeat, muscle tension, stomach or digestive troubles, shallow breathing, along with many others. It is also often characterized by spinning thoughts that generally include what we call cognitive distortions (or thought errors) that we all experience, just a bit more intensely. Where we actually experience the sensations of anxiety stem from our central nervous system (CNS). The CNS is found in all mammals on the planet, and is a built-in protection system to help us keep us safe when we are in danger. The fight/flight/freeze/fawn system, as it's often referred to, allows us to respond in whatever way we need in the moment to survive. We don't want this system to go away, as it serves a very valuable function (for example, we want to be able to respond if a wild animal finds their way into our home). However, when many of us experience anxiety today, we are not currently in physical danger, though our same internal alarms can sound. When our CNS is misfiring consistently (or is dysregulated, in other words) it can have a pretty significant impact on our lives.
"How can I feel more comfortable?"
As mentioned above, we don't necessarily want all of our anxiety to go away. What we do want, however, is for it to feel less overwhelming, feel like we can manage through it, and to occur at appropriate times. There are many effective ways in to manage anxiety, including examining and balancing our thoughts (through cognitive behavioral therapy), learning mindfulness strategies (which eventually, after some practice, helps us to be present enough to intentionally observe our thoughts so we can actually balance them), along with discovering what our bodies need (breathwork, stretching, walking, etc.) to help reduce physical symptoms of anxiety. These three strategies, when used together, help better regulate our central nervous system and eventually give us more of a sense of connection with our bodies which, in turn, helps us feel like we have a bit more of a say in how we feel day to day.