Identify moments when you haven't felt detached, then factor more of them into your life – whether it's going for a run or playing with a pet. There will be things that light you up.
Music and physical movement can help ground you in reality. They make the world around you more impressive than what's going on inside you.
Don't ignore it – accept that you're feeling detached and disconnected. Acknowledging your lack of emotion may help you feel more in control of the situation.