For a non-native English speaker like me, it's always been hard to sound æ and ɛ differently. For example, "salary" and "celery" are two words that I tend to pronounce identically.
Is it OK to go on like this or should I practice to get it right?
Here is a typical English vowel chart:
As you can see, /æ/ and /ɛ/ are quite close to each other, and so have quite a similar sound. The difference is in the degree of openness: /æ/ is “near-open” and /ɛ/ is “open-mid”. If you want to make a clear distinction between the two, you need to practice, practice, practice. When I was learning phonetics, I found the best practice was to try to make long continuous vowels that go along the axes, like /iiiiiiiieeeeeeeeɛɛɛɛɛɛɛɛææææææææaaaaaaaa/. Once I was able to master making the entire continuum, it became easier to find individual points along the continuum.
@Mehper C. Palavuzlar The easiest thing you can do in keeping the difference between [ɛ] and [æ]is to pronounce every [æ] like [a]. I know most people don't even realize a simple fact that for most British people [æ] is quite a foreign sound. In the Midlands, Northern Britain, Scotland, Wales, Ulster and Ireland [a] is the most usual, typical realization of [æ]. The same is true for both Canadian and Caribbean dialects &/or accents.
The most dictionaries I consulted show that the first e in celery is IPA e (seləri).
Read what the important phonetician Daniel Jones said about æ
The correct sound of æ can generally be obtained by remembering that æ must have a sound intermediate in quality between ɛ and a. In practising the sound, the mouth should be kept very wide open.
The sound may be obtained by imitating the baaing of a sheep which is very like ˈbæː . Those who are unable to obtain the exact quality by practising such exercises should note that it is better to err on the side of a rather than on the side of ɛ (my emphasis) . a is actually used for æ in some parts of the North of England. (Note 401 in this book).
I also noticed the emphasized part from my own experience with words such as happy and laptop.