Is sage leaf and B12 good for anxiety?

Neither sage nor B12 are used specifically to help anxiety. 

Sage has a variety of actions but is traditionally used for treating excessive sweating and hot flushes.

B12 is a complex nutrient with a variety of actions including helping to maintain a healthy nervous system and some people do become deficient through various health conditions.

In general the nutrients used to help anxiety include B vitamins (as complex of the various B's used together to ensure balance within the body) Magnesium as well as Zinc and Vitamin C. 

Click on this link - http://www.health-alternatives.com/vitamins-nutrition-chart.html - to find a list that shows food sources of vitamins which you may find helpful or you could add these in supplement form and discuss recommendations with your local health store.

In terms of herbs, Passiflora Complex has been used traditionally to support the nervous system by easing stress and nervous tension. It takes up to a week to feel the effects and if you have not noticed an improvement after a month, then we suggest exploring an alternative.

Relaxing Essence may also be worth considering. This is a blend of flower essences which can balance emotions where feelings of pressure, anxiety or fear have been a problem. 

Best wishes.