It is bloody difficult when they're this age, was thinking this today. Ds does not stop. Not for a second, he runs between tipping a basket of toys over, to resetting the washing machine mid cycle, to escaping up the stairs if he gets a sniff that the gate is open. He's lovely, but seriously hard work and I don't get any help as dh works away and the IL's aren't too interested in getting their hands dirty. My family is a long way away.
It is relentless, don't feel bad for struggling, I think we all do. I've never found anything as hard in my life as dealing with a 3 and 1 yr old and my job was pretty demanding and stressful.