3 sentences

1. 回首往事，他感慨万千。

   huí​shǒu wǎng​shì, tā gǎn​kǎi​wàn​qiān.

   Looking back on the past, he was filled with deep emotion.

   Source: Dong Chinese Dictionary

2. 谈起那段往事，他总是感慨万千。

   tán​qǐ nà duàn wǎng​shì, tā zǒng​shì gǎn​kǎi​wàn​qiān.

   Speaking of those past events, he is always filled with deep emotion.

   Source: Dong Chinese Dictionary

3. 回顾过去十年的奋斗历程，他感慨万千。

   huí​gù guò​qù shí nián de fèn​dòu lì​chéng, tā gǎn​kǎi​wàn​qiān.

   Looking back at his struggles over the past decade, he was filled with emotion.

   Source: Dong Chinese Dictionary