He must be a great guy, because I can just imagine it must have been hard to let someone into your heart again.
I believe I've heard the use of 'just' in similar sentences. Is it correct and what is its use?
The given sentence is okay. The word "just" is often used like this in English, as a non-essential intensifier or qualifier - it can be omitted from the given sentence with no loss of sense. Other examples of this kind of non-essential use of "just" (it can be omitted from all of them with no loss of sense): I just can't imagine how you could let someone into your heart again after being hurt so badly.
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The given sentence is okay. The word "just" is often used like this in English, as a non-essential intensifier or qualifier - it can be omitted from the given sentence with no loss of sense. Other examples of this kind of non-essential use of "just" (it can be omitted from all of them with no loss of sense):
I just can't imagine how you could let someone into your heart again af
Verbs of imagining (e.g., imagine, see, hear, picture) are used with 'can just' in that way.
I can just imagine his reaction.
I can just hear the roars of laughter.
I can just see her face when he told her.
I can just picture how hilarious that was.
Another series, without 'can', involves verbs of love and hate.
I just [love /