Using a thesaurus can be great for broadening your vocabulary, finding better and different words to say what you mean and avoid clumsy repetition. It can also lead to you using totally inappropriate words in completely the wrong context!
For example, I've just looked up "context" in the MS Word thesaurus, and it's given me the following options: background, circumstance, situation, framework, milieu, perspective, environment. If I was looking to replace the final word in my first paragraph, there's only one of those seven that really fits. So always be careful about using alternatives from the thesaurus if you're not sure how they are used within the natural language - beware of words you don't know, and particularly beware if English (or whatever language you are writing in!) is not your first language, because there are often nuances and subtleties that dictionaries, thesauruses and translators don't manage very well.