Rose76, I am so sorry to hear of the loss of your SO. They must have been such a big part of your life for you to have so much emotion after their passing.

This lists many articles about coping with grief. Coping with Grief | Psych Central
Perhaps one of them may be of interest to you.
Five Coping Skills You Need to Work Through Grief

Sorry somehow the icon was selected down the bottom of your post and I took it off .

You say that you fear that you may have a re-occurrence of the dark feelings you experienced after their passing. If you ever find yourself in crisis, these links may be a help to you.
Get crisis help online right now via chat:

CrisisChat - Home

On your smartphone:

Crisis Text Line | Text HOME To 741741 free, 24/7 Crisis Counseling

Or through a telephone call:

Lifeline
http://www.suicide.org/
http://www.hopeline.com/
http://www.suicideforum.com/

I have felt the emptiness of losing a loved one and it is not something easy to get through. One thing I had to do was change the focus of my life and reinvent my self concept since much of my pain was wrapped up in that relationship. I did find a grief support group and talking to a therapist helped me find a new life. Call your insurance company if you need a referral or check their website.

Hope you get the support you need.
@CANDC