You said, all your feelings start bubbling up. So that sounds like more feelings come to the foreground other than existential dread. Maybe those are important too. In that case you could ask yourself what kind of feelings those are and maybe try to just sit with them and notice how they go away or become less intense after a while.

Existentialist philosophy recommends accepting existential dread/anxiety/absurdity as the only way to live an authentic, free life in which we might eventually build our own meaning. Monist philosophies (like mystic tendencies) emphasize the interconnectedness of things and maybe find comfort in seeing separation as an illusion.

Any way, accepting your feelings without judgement is good in general. And like others said, mindfulness based meditation might help.

Disclaimer: in case of existing traumas, mindfulness meditation can be dangerous to try alone, as it might cause people to relive their trauma. And in case of depression, it might not be enough on its own without cognitive behavioral therapy or addressing underlying causes.