[sbaqai]

This is not that big of a problem and I think to varying degrees, everyone does it. Learn to spot when you do it more frequently. And for practice, make a note when others do it as well. You'll learn to distinguish air-tight arguments from sloppy ones. It also helps to use a mental filter to call yourself out before anyone else can. Here are things that help me:

1/. State an argument. Then, take the opposite side - ask yourself, what are the arguments people might have against my argument? What assumptions am I making? Is what I am saying true in all cases or only under specific circumstances?

2/. Reading Richard Feynman's Cargo Cult Science speech at Caltech helped: http://www.lhup.edu/~DSIMANEK/cargocul.htm

3/. Two quotes from Charlie Munger (Warren Buffett's partner), that also act like a filter:

"You are not entitled to an opinion unless you can state the arguments against your opinion better than your opponents can."

and from an interview:

Q: You've often said that one of the keys to your success has simply been to avoid making the garden-variety mistakes that you see other people make.

Munger: Warren and I have skills that could easily be taught to other people. One skill is knowing the edge of your own competency. It's not a competency if you don't know the edge of it. And Warren and I are better at tuning out the standard stupidities. We've left a lot of more talented and diligent people in the dust, just by working hard at eliminating standard error.