It's hard for me:
"It is hard for me to be pleasant to annoying people." hard = difficult
It's hard to me:
A: "Feel this, it is soft."
B: "Soft? It is not very soft at all."
A: "No, it is soft! Feel it!"
B: "We disagree, it is hard. Well, at least, it's hard to me." Hard = solid, unyielding
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