Your mind is either racing - frantically trying to work out how close the latest explosion was, whether it was a missile or a rocket, a one-off or part of a salvo - or wondering how long it might be before the windows shudder again and the screaming blare of the air raid siren sounds.
But if visitors like me, on my third trip to the city since the war began, find the long nights challenging, how do local people - who reckon they have had just 20 or so quiet nights since the war began - possibly cope?
"Sleep? Not much," said the manager of our hotel one morning last week. She had seemed irrepressibly energetic in March, racing past the boarded-up windows to show guests the makeshift bomb shelter in the cellar.
But now her face betrayed the exhaustion that appears to be overwhelming much of Mykolaiv.
"I don't have my own cellar at home. It's flooded. So, we've nowhere to hide. We just lie there in the dark. Last night the explosions were the closest yet - a couple of blocks away," she said.
Once ordinary noises, like a slammed door, or a growling truck, are now loaded with terror, as people brace themselves, instinctively, subconsciously, and permanently, to react to anything that might sound like a missile, or a plane.
"Me? I've been trying to go to bed early. Around 7 or 8pm. That way you get a few hours before the booms begin, if you're lucky," said Gela Chavchavadze, 60, the owner of a café that delivers free cooked meals, most mornings, to neighbourhoods bombed the night before.
The explosions usually start soon after midnight. Artillery fire from Russian positions to the south, rockets from behind the frontlines further east, jet-launched bombs, and devastating cruise missiles thought to be launched from ships in the Black Sea and beyond.
Sometimes there's a specific target, but - whether by accident or design - the blasts mostly occur in residential neighbourhoods and with a blitz-like randomness that turns every night into a nerve-shredding mind-game.
Over the past week the Russian bombardment - including several day-time attacks - has reached a new level of ferocity.