sometimes speaking english is much more suitable. it really doesn't matter, that vocabulary underlines each word I've just typed with red. every single word carries a huge cargo of meaning- maybe this is because you understand foreing language in different way than your own. you look deeper through the word to the meaning itself it carries. it is much more interesting to watch a film on english- only in this way you can understand all the meaning of every phrase... of cause if it is english film)
another situation when it is better to speak english for me is when it is difficult to talk on russian. for example when it touches some events in my past, that I'd better haven't spoken. or about feelings, but this is much rarely. because speaking about feelings should be understood by both speaker and leastener.
Also my thoughts gonna crazy sometimes, they build novels in my brain and on english only. sometimes i even write them down to the paper... but be quite ;) this is secret.