If we've been "numb" "zoned out" "disconnected" or "deadened" it can be overwhelming to begin to feel again.
I remember a client I worked with a long time ago, who had been quite disconnected from herself for decades. As a result of her work in therapy she was beginning to "come alive" again, beginning to feel her emotions.
Not only did she experience her emerging emotions as challenging, physical experiences were too. For instance, she once came into our session panicked. She felt physically tired, had a runny nose and a bit of a cough. She had never experienced a cold before, and it's symptoms felt frightening and chaotic to her.
As we gain experience with our physical and emotional selves we become more familiar with what both of these aspects of ourselves are like and what we can expect in the future. And, we become more confident that those emotional and physical sensations can exist in us without becoming overwhelming and/or harmful.