Can one improve his/her English skills?

Definitely, one can improve his/her English skills. It is just a matter of effort and determination.
There has to be determination in order to acheive results. For instance, as reading does helps improve English, he/she has to get a book to read, and have the determination to finish the book.
And then there comes effort. Other than having the determination, effort has to be put in otherwise, sloppy results could be obtained and of course, that is undesirable.
Everyone has the ability to improve his/her English skills. It is important to work hard and never give up. No procrastination as well!!