Find something or someone that you truly, utterly, deeply care about. Think of all the ways that the subject could be damage, lost, killed, defected, or otherwise negatively impacted. Vola--instant anxiety!
If this is successful, then I apologize for any discomfort it may bring.
Perhaps what you really need, though, is more energy, excitement, or motivation. Those things seem very much like anxiety in terms of expression and feeling, but they are of different origins. Energy stems from a healthy body and a healthy mind--eat well (fruits, veggies, ect.), exercise, meditate, and enjoy life. Excitement comes from the anticipation of something positive or the accomplishment of something grand. Motivation is similar to excitement; its an inspiration that can drive you to accomplish. Think of all the wonderful things that you could become. Think of all of the spectacular things that you are capable of doing. Find something to inspire you to become the best that you can possibly be. Perhaps this can give you the "feeling" that you believe that anxiety can provide for you.