我不想纠结于过去。

I don't want to ___dwell ___on the past.

纠结于小的挫折是没有成效的。

It's unproductive to ___dwell ___upon minor setbacks.

她经常纠结于自己的失败，而不是继续前进。

She often ___dwells ___on her failures instead of moving forward.