The following is a technique for writing deeply-felt character emotions, as described by Donald Maass in his book The Emotional Craft of Fiction. It's the single most valuable thing I learned about writing fiction in the last year.
Step One
Pick a moment in your story when your character feels something strongly. Identify that feeling and write it down. Then dig deeper. What else are they feeling? Write down that second feeling. And what else are they feeling beneath that? Writing down that third-level emotion. You should now have a list of three emotions.
Example:
Fear
Vulnerability
Loneliness
Step Two
Work with feeling #3 and examin