This is an unusual question, because sometimes it's not helpful to lighten the mind after having a deep death meditation even if it gives you a bit of a heavy feeling. That heavy feeling can actually be used to stimulate what's called "Samvega".
Samvega is a Pali word which in English generally means "a feeling of urgency", a feeling of getting on with something. Now, when we're contemplating death, when we think about it deeply enough, we often start to realize, "yeah, I could die today, that's right! I could die today" Now most of us don't like thinking that way. It becomes a heavy feeling of "Uh, I could die today. Now what can I do to lighten the mind, I don't want to think about dying today!" Wait a minute; thinking about it can be helpful. Don't be so quick to get rid of it, it's really only going to bring about benefit.
So you could die today, you're feeling a heavy feeling, what are you going to do about it? What are you going to do about it? If you want to reflect on any subject that's going to work and deepen it, what are you going to do about it? Now whether it lightens it or not, I'm not too worried about that, you'll come out of it after a while, you don't have to be too upset. But if you want to take it in deeper, that you're going to die today, what are you going to do about it?
Once I saw a screensaver, the ones where you can type in whatever message you want, and it ran a message across the screen which said: "If today is your last day, how do you wish to be remembered?" Something to think about, how do you wish to be remembered? So, if you're having a heavy feeling about the possibility of death, use that to stimulate doing something more in your life. Do something more in the Dhamma, do something more to be a better human being, to make more good Kamma, whatever it is, use it to stimulate that Samvega feeling of getting on with the practice.