I think for me it's not hopping on the trend that I regret but diving too deep into one. For example I really liked puffed sleeves - and I still like them - but I have four puffed sleeve pieces - I think I overdid it.
Another example (from a while ago ) was the tunic over legging stage with ballet flats. I overdid it and kept trying different variations to make it work on me (from memory I recall four different tunics and four different pairs of ballet flats). One of two of them worked okay but I should have left it there.
I mostly now try and think about just one thing of that genre - the power of one. That way I don't end up with three or four pieces from a look I am tired of, but just one that I hopefully have almost worn out.
But I missed that on the puffed sleeves trend...thinking one was a dress, one short sleeved blouse, one long sleeved blouse and one a knit!