Anxiety is what we feel when we are worried, tense or afraid - particularly about things that are about to happen, or which we think could happen in the future. Anxiety is a natural human response when we feel that we are under threat. It can be experienced through are thoughts, feelings and physical sensations. Common anxiety signs include: nervousness, restlessness, panic, increased heart rate, breathing rapidly, sweating, trembling, feeling weak or tired, and trouble concentrating.