John Sutton netted the only goal as early as the fifth minute and Shiels said: "To get booed off at the end is brilliant.
"It makes me feel so good because it's testament to how far we have come - to lose 1-0 against Hearts.
"That's testament to the expectations of what supporters are seeing.
"Sometimes it's frustration and I understand it. It happens to all of us in our work and what we do."
Shiels was frustrated by Mo Sissoko whose error allowed Hearts to take the lead.
He added: "Everybody starts at three o'clock, he starts at 10 past. He deserves criticism. He went to sleep.
"We were the better team in the second half but Hearts dug in.
"The shape was much better in the second half and we created chances for the forwards but we just didn't finish.
"In life in general you have to take defeat on the chin and realise it's not going to be your day."