안 먹어 vs 못 먹어. These are quite different in Korean. The first means you made a choice, the second means you had no choice. So, you might hear 못 했어 for something and know it's a bad excuse!
늦게 일어나서 시각에 도착을 못 해요. - I got up late so I can't get there on time. 늦게 일어나서 시각에 도착하지 않아요. - I got up late so I'm not coming on time.
Either way, it's your fault. The first way makes you sound more pitiful, but the second way makes you sound careless.