When I learned English at school (in France), my teachers asked me to make effort to have an "England-like" pronunciation (which was difficult for me).
Today, I use the English language for my work (technical English, mostly) and I noticed that I was often better understood when I did not put effort into my pronunciation.
When speaking English, will you be better understood by most people (English native or not) if you force yourself to pronounce your words in a particular native accent, or if you speak more smoothly in your foreign accent?
Put another way, how much effort should you devote to improving your accent, as opposed to your vocabulary, grammar, or other aspects of the language?