constrain指“强迫(某人做某事)”；restrain指“控制、限制、约束(某人做某事)”。前者接带不定式的复合宾语；后者可接名词、代词或宾语＋from doing sth.。

• His father constrained him to write and ask for your forgiveness.
  他父亲强迫他写信请求你的宽恕。
• Let's restrain ourselves from arguing any further.
  咱们都忍着点吧，别再争了。
• She couldn't restrain her curiosity to see what was in the box.
  她无法控制自己的好奇心，想看看盒子里有什么。
• The police had difficulty in restraining the two men from fighting each other.
  警察费了很多事才控制住两个男子，让他们不再互相殴打。