Here you are telling someone that you feel strongly about doing a particular action. Here are some examples:

在这里你是想告诉别人你强烈地要做一件事，这里有一些例子： 

"I think I should practice my reading."

 我想我应该练习我的阅读。

"I think I should join a study group."

 我想我应该加入一个学习小组。

"I think I should handle this as soon as possible." 

我想我应该尽快处理这件事。

"I think I should earn my degree."

 我想我应该获得我的学位。

"I think I should explain myself."

 我想我应该解释一下。

By adding the word 'don't' you have changed what you are conveying from something you are thinking of doing, to something you are against.

通过加'don't'这个词你就把你想做的事情变成了你不想做的事情。

Here are some examples: 这里有一些例子： 

"I do not think I should complain so much."

我想我不应该抱怨这么多。

"I do not think I should attend that event."

 我想我不应该参加那个活动。

"I do not think I should borrow more money."

 我想我不应该借更多的钱。

"I do not think I should doubt you."

 我想我不应该怀疑你。

"I do not think I should decide until later."

 我想我不应该后面再决定。