While it's incredibly tempting to fill the space with over-thinking or getting busy DOING something when you're feeling flat, empty, bored or dead inside, try to resist.
Deep breathing for 2 minutes and rubbing/massaging or patting where you're feeling those sensations while STAYING COMPLETELY OUT OF YOUR HEAD, will spawn the fastest emotional growth you can possibly gain.
Think of your Core Self as a huge, blank artist's canvass. Whenever you let yourself feel any type of emotion without getting your mind involved with it (even to where you wanna identify or name it), you are BUILDING your emotional repertoire.
Think of your emotions as different colors of pigment. There are warm colors in your collection of paints, and cool ones. All these hues make up distinct parts of you. They each represent diverse aspects of your personality.
To judge, shun or despise certain emotions, means you hate parts of your Self. ALL the colors of you are beautiful and good. There's no such thing as a "bad" color, or a bad or wrong emotion. These are all the facets, aspects and parts of your very human BEING.
Learn to accept them. Learn to endure them in the body. Allow yourself to embrace them FULLY. No part of you is unacceptable, no matter WHAT you were taught as a young child, by a dysfunctional parent.
Deep breathe into your emptiness. It's not easy, but you will survive and get to the other side of it. You'll shrink that core void a bit EVERY time you do this exercise! Eventually, your inner 'blank canvass' will be splattered with magnificent colors both light/warm and dark/cool and everything in-between~ and your emptiness or flatness will gradually diminish and ultimately, mitigate.
Give yourself TIME to practice this technique. You can only get better and stronger, if ya do. You will start to feel a sensation of aliveness you've previously had to depend on dysfunctional others to catalyze for you. That won't happen anymore, because you are feeling more at ease, hanging out with YOU now. Amen.