I Don't Know How to Break Down My Defensive Wall

It's rare that I actually have anything serious to ask, but i'm sort of lost on this one.
I've been through a lot in life and i'm a strong person from it, but recently i've realised I find it difficult to feel compassion for others. My actions are compassionate as my values are that way, but I used to be able to feel emotions very strongly. I think i've got very strong defence mechanisms, if people feel peaks and valleys i feel mostly flat, i'm not depressed though at all.

So the question is, how do you get in touch with your emotions again?/what did you do to help that?.