This is a rather thorny subject, since like everything else, not even we translators agree about it. Opinions are divided. Some translators think that they themselves can make their own raductions and do not need help from others, it is a very respectable point of view, but that I personally do not share.
From my point of view, I am not infallible and I am not exempt from making mistakes, I am human, my mistakes do not mean that I do not know how to translate, I know what to do, but I will explain with an example that sometimes our judgment is may cloud a little. When you have been introducing a lot of time into another language. In the language, which clients are constantly requesting to translate, for example from English to Spanish, when you finish translating the text, apparently for you as a translator is fine and looks perfect, but when another translator reads your translation, the other translator apart from bringing you new ideas, he / she finds that your translation is not read in a fluent Spanish , which looks like a Spanish machine.
I believe it never hurts to ask for help, the previous example has happened to me and many times my colleagues say “your translation does not look as if it were in a correct Spanish, it is a weird Spanish”. I never took it wrong, so when they can correct me, I thank them very much, because every correction is recorded in our memory, it helps us to improve, but we are not knowledgable, the language is very broad to learn everything about it.
Another inconvenience is the misunderstanding of some clients, who think that the translator is a machine, not a person and prefer to skip the process of correction in the translation, forgetting that translation is a process and, it has its steps which serve to help solving problems, that arise within the same translation and deliver a job with a very good quality.
Correction is a complementary and much needed process in translations, so if you are going to ask for translations, it is preferable to wait a little, but with the certainty that you will have a translation with many less errors, that if a single translator makes his /her own corrections.