1. I've made a tough decision,sir. Here is my resignation.
我做了个艰难的决定，这是我的辞呈。

2. I quit because i don't want to be stuck in a rut. I want to move on.
我不想陷入窠臼所以才辞职。我希望能向前迈进。

3. First of all, I'd like to say that I've really enjoyed working with you. However, I think it's about time for me to leave.
首先，我要说的是，我真的很高兴能和你一起共事。但是，我觉得该是我离开的时候了。

4.I've been trying, but I don't think I'm up to this job.
我一直很努力，但是我觉得自己无法胜任这个工作。

5. I've been here for too long. I want to change my environment.
我在这儿待得太久了，我想换一下环境。

6. I'm sorry to bring up resignation at this moment, but I've decided to study abroad.
很抱歉在这个时候提出辞呈，但是我已经决定出国念书了。

7. To be honest, I've got a better offer.
老实说，我有一个更好的工作机会。

8. I'm running out of steam. I need to take a break.
我精疲力竭了，我要好好休息。

9. I'm quitting because I want to try something different.
我辞职是因为我想尝试不一样的东西。

10. I want to expand my horizons, so I've put in my notice.
我想拓展自己的视野，所以我辞职了。