Don't put off responding to a message.
Ask how you can help during an anxiety attack.
Understand that situations that appear simple and easy in your daily life may be tough for someone with anxiety.
Make concrete plans whenever possible.
Help them remember positive memories and entertaining thoughts.
Learn to notice their signs of an oncoming anxiety attack.
Suggest activities that will make them feel better.
Don't say things like "You weren't always this anxious" and "Why are you so complicated?"
Help them understand that they're not abnormal.
Talk with them about what makes them feel anxious.
Don't create unnecessary suspense.
Invite them to spend some time doing "nothing" with you.
Be someone who an anxious person knows they can count on when things are bad.
Understand that someone with anxiety may also need space.