United have conceded the first goal in their last four league outings and they were left with a mountain to climb again after Michael Higdon and Chris Humphrey both scored in the opening 10 minutes.
Jon Daly cut the deficit before the interval but despite laying siege to the Motherwell goal after the interval there was no way back for the Terrors.
"It's beyond a joke, that's four of the last five games in a row that we've fallen 2-0 behind and you aren't always going to be able to fightback," said Houston.
"I don't know why we need to wait until we are 2-0 down to start putting tackles in - it's very frustrating.
"We got the goal back before the break and that gave us a lift, I honestly believe we deserved to take something from the game and dominated the second half.
"I can't fault the players effort or commitment, but you can't give teams two goals of a start."