My boyfriend is depressed, how can i support him?

been with him a year. in the last 6 months he has been on a course to get a promotion at work.he has gone for the position before but pulled out because he was scared of failing. he said i gave him the support he needs to try again. i think he is trying to prove himself to me, to better our future, but i said he has to want to do it for himself not us. anyway, he is so stressed at work and he is forever tired or snappy and he doesn't seen to want to make love to me as much. we are going on holiday next week. how can i save our relationship? thanks x