Prevention is better than cure.
I completely accede to this state because of some reasons.
I believe a paragraph has a beginning, especially formal or ideological one. You said you acceded to the statement (notice the use of "state" is initially inconceivable, perhaps doubt-arousing that the composer uses dictionaries during practical session of phrasing), though, as I notice, the statement is not brought up nor identical to any precedence. Avoiding such incomprehensible errors saves much points at times of marking.
Firstly, If people know how to prevent diseases such as cleaning hands regularly, eating a large amount of fruits and vegetables, doing exercises, do not smoke or drink alcohol much ...they will be healthy and happy. Consequently, they are full of energy to do whatever they want. On the contrary, if they do not care about how to avoid sickness, then when they get sick, that wil cause them many problems. For instance, they have to suffer from plenty of pain. If worst comes to worst, illness can lead to death.
The phrase 'diseases such as' is, linguistically saying in consideration of the purporting instances that follow, absurd i.e. ridiculously unreasonable. Notice that you can prevent diseases BY (not 'such as') cleaning hands regularly, etc, etc. An unreasonable, not-yet-proofread version of prepositions may result in meaninglessness or incoherence of arguments. Also, examples taken up and marked in red tell that you have not a careful scrutiny into your arguments and further prove that you may probably be referring to thesauruses--as referred to in the comments for the first paragraph.
Furthermore, the phrase bold-in-red proves clumsy in language usage and lackluster in other phases. A four-word phrase should be altered to two words' worth of reading, for prolonging such sentences/phrases/etc. is rather senseless and frankly worthless. Finally (at least considering lexical need), the word in bold itself demonstrates a fair need to be refined.
As for the content of the paragraph to say, arguments come with examples: yours lack examples--specific examples.
Secondly, it is so good if every one prevent diseases by being examined by the doctors frequently as many serious sickness can be cured successfully when dected in an incipient stage. Moreover, ill health can make people get into financial problems since treating process usually costs a gigantic amount of money.
Reddened words and phrases are noticeably clumsy. 'so good' is lackluster; often I find 'being examined by the doctors' an awkwardly written phrase. Perhaps 'going to the doctor' is a better, more sound affirmation of words. 'make people get' is rather unlikely: for it can be rephrased as 'get people.' Also, 'treating process' is rather enduring: changeable to treatment, fitting yet the sentence more deeply sound.
Generally speaking, every one should find out good ways to avoid illnesses rather than cure them.
Note that 'every one' should be, in modern dictation, 'everyone' without any space. Perhaps it is a small piece, but such pieces often prove of great importance once it comes to marking. The noun 'illness' is, throughout your composition, parallel i.e. they are not the same in places. Such tasks of maintaining same notions (as to whether illness is countable) are rather valuable, for it marks a careful person, and gives out good signals to the judges.
Your essay, if I may say so, appears lackluster in many ways, yet in some ways it is particular. Your vocabulary proves worse and worse as the essay proceeds, but a good range of peculiarity--for I notice, since 'state'--is used as a good tool.
I anticipate a better writing next time.