说 to the best of one's ability“总是”放在句末，有点绝对，应该说“通常”放在句末吧。关于 to the best of one's ability 在句中的位置大致可按以下情况处理：

1. 如果 to the best of one's ability 修饰的是不及物动词，即动词后面没有宾语，此时 to the best of one's ability 自然就在句末了。如：

Every game, we go out and play to the best of our ability. 我们每场比赛都倾尽全力地去拼。

I’m sure he’ll do the work to the best of his ability. 我相信他会尽己所能做好这项工作。

2. 如果 to the best of one's ability 修饰的是及物动词，但它的宾语比较短，此时 to the best of one's ability 通常会放在宾语之后，此时自然也就在句末了。如：

I take care of them to the best of my abilities. 我尽全力照顾他们。

Just try to do the job to the best of your ability. 试尽你所能把这项工作做好。

3. 如果 to the best of one's ability 修饰的是及物动词，但它的宾语比较长，此时 to the best of one's ability 既可能放在宾语之后（即句末），也可能放在宾语之前（即句中）。如：

We must exploit what we have to the best of our ability. 我们必须尽量利用我们拥有的一切。（位于句末）

He always participated to the best of his ability in whatever they were doing. 他总是尽量参加他们所做的任何事情。（位于句中）