Source: Swan. M. 2005. Practical English Usage Oxford, United Kingdom: Oxford University Press (2011).
Practical English Usage lists over a hundred common mistakes in the English language. Even very advanced students of English can make mistakes – nobody’s perfect! Swan (2005) has listed a number of them.
“I wish you felt / would feel better tomorrow.” = I hope you feel better tomorrow.
(630.3) Wish + that-clause is not generally used for wishes about things that seem possible in the future. We often use hope in this sense.
“The train may be late, as it happened today.” = The train may be late, as happened today.
(581.1) Than and as can replace subjects in clauses (rather like relative pronouns).
“When I wrote my letters, I did some gardening.” = When I had written my letters, I did some gardening.
(424.1) We can use the past perfect with after, as soon as etc to emphasise that the first action is separate, independent of the second, completed before the second started.
“When I had opened the door, the children ran in.” = When I opened the door, the children ran in.
(424.1) We can use time conjunctions (e.g. after, as soon as, when, once) to talk about two actions or events that happened one after the other. Usually that past perfect is not necessary in these cases, because we are not ‘going back’ from the time that we are mainly talking about, but simply moving forward from one event to the next.
“Stefan can never return back to his country.” = Stefan can never return to his country. / go back to his country.
(87.3) When the verb itself already expresses the idea of ‘return to an earlier situation’ or ‘movement in the opposite direction’, back is not generally used.
See other: Notes On English Grammar