To my somewhat limited mind, wholeness involves the merging of the conscious self with the universe.
I believe that all of us are already whole, it's just that most of us don't allow ourselves to realize this wholeness, instead we just experience it in snippets.
Now it's possible to overthink what 'merging one's self with the universe means, quite easy to overthink it in fact, because as soon as you start thinking about it, you miss what it is, but we all have a sense of this merging feels like.
Probably for most of us this experience of the 'self merging with the universe' will have come in the form of merging one's self with some kind of kind of aesthetic/ creative experience - such as dancing, or art, a state commonly referred to as 'flow', a state where you are conscious in the moment and happy in that moment.
Another means of merging with the universe is through empathy with others - when helping others, or raising children (I assume) one at times will lose one's self by putting the well-being of another self at the fore.
These two means of realizing wholeness through merging the self with the universe - namely mindful embodied practice and compassion can be practiced all day, every day by anyone, in any situation.
Those two practices are really all we need to be whole, maybe along with some formal meditation to allow the practice to intensify.
An important part of the empathetic/ compassionate realization of wholeness is to remember that we're all in the same shit together - all of us with our little fragmented egos struggling daily with the many miseries of this limited human life - all of us desire a greater sense of wholeness, or deeper connection with the universe, and there are many ways we might realize this.
Instead, however, too many of us focus on the differences between our little 'selves' and spend time struggling to get those selves recognized by others - maybe through conspicuous consumption, maybe through seeking attention on social media, maybe through violence, which is a shame, because this is a lose-lose situation.
Thankfully, all we need do to be whole is be patient in our daily practice, patient, mindful, compassionate, and not try to do too much - we are already one with the universe after all, we are already whole, we just need to allow ourselves to realize it.