Yes it is. Although, I'm not sure why from a technical standpoint. It might be that when you guide something the to is implied.

We need time to prepare a dinner, to go to somewhere we want to go and so on. Almost everything needs time to be finished. So if you set up a goal, no matter if it is hard or not, please do not be anxious. Do not try to push yourself to skip the important steps therein. That is what I should remind myself: every time I lose the opportunity to my incompetence; I would be anxious. So I have to remind myself of that, and keep it up.

And Maybe there are some things you cannot change even though you have sufficient time. For instance, trying to be the person who likes to do household chores. That is why my house is invariably messy. It will become disordered soon after I tidy it up. Oh.
Good night.

The people among the Korean peninsula are kindred people. Why do they not stop the conflict？

なぜ朝鮮半島の人々は同種の民族なのに、紛争をやめないのだろう。

Cancer cells are one of the famous subversive elements for our bodies.
がん細胞は体を破壊する有名な要素の一つである。

People who are anemic, should take meals that are rich in iron.
貧血状態の人は、鉄分の多い食事をとるべきだ。

I want to find the jobs attuned to my career.
私は自分の経歴にあった仕事が欲しい。

I dislike my bundling ways while writing essays in English. I am not sure what the meaning of this sentence is, therefore I cannot correct it.
私は英語のエッセイの手際の悪さが嫌いだ。

I added a comment to this correction, explaining why "the Korean peninsula" was needed. All in all though, great job.