It's OK to Fold Top Pair (tourney)

Here are two examples that exemplify what can happen with top pair. One shows a good fold by me, and the other shows why I should have folded.

On the later hand, I knew I had one player beat, and if the big stack had folded, I would have had some chips left and survived. But for some reason, it seems like the big stack tends to be luckier than other players. Nevertheless, I guess I lost my concentration and just made a terrible error. The lesson is to always stay alert, especially during tourneys since one mistake can send you packing.