wow, xtinee, you are such a good korean speaker! your question is always 항상 어렵다... ㅠㅠ
your question are 언제나 어렵다!
my answer is, totally the same meaning.
항상 : always
언제나 : all the time
often : 자주
자주 is often, it's like almost. like 80% but not 100% or 99%.
항상, 언제나 are almost 100%, or 99.9999%. that's 항상 or 언제나. always or whenever all the time.
hope it helps