When choosing essential oils you have to take everything into consideration to select the blend. But I can give you some general advice. (what I means is that you need to get to the root cause of the problem! ie sadness, grief, anger etc etc) different oils will help.
Bergamot is the BEST oil for uplift. it is wonderful for depression. If you combine it with orange and petitgrain it will help. But also other oils that can be blended with it or used alone or with others are; lavender or chamomile (to relax) geranium (to balance) jasmine or rose otto, clary sage (fantastic for stress, but don't drink that day).
That will give you something to go on and I am sure the others will contribute.