Ciao Ferdaous, In the Italian language is not necessary use the pronoun because every verb has different ending parts in the congiugation, so it's impossible to confuse one with another. Ex. io abitO, tu abitI, lui abitA, noi abitIAMO, voi abitATE loro abitANO. no one in similar to another (we could say that the pronoun in inside de ending so we don't need to say or write it)

Italian is a language with a high degree of redundancy. This, as Sara already pointed out allows ALMOST OFTEN to drop the subject of verbal voices, and it also allows different part of the sentence to (more or less) freely move around, as the many propositions used will clarify the meaning in any case. Usually we DO NOT drop the pronouns /loro/ and /voi/. You can keep the pronouns in other case, which fact usually (but not always) leads to emphasis, and the exact meaning of the emphasis depends upon the context. Examples: -- posso dire che io sono onesto (possible meaning of the emphasis: I am not sure about the others). -- io non voglio piu` aspettare (possible meaning of the emphasis: I'm also getting angry) -- noi accendiamo tutte le sere la TV e ascoltiamo il telegiornale (possible meaning of the emphasis: TV is making us dumb, we act as a flock of sheep)

Both are grammatical correct, we italian people omit the subject often just for custom, for example: Io sono stanco, stasera non voglio uscire Sono stanco, stasera non voglio uscire both are correct, but we usually say the last, wheras the subject may be included when we need to put more stress on it: Io sono quello che porta i soldi a casa = I am the one the brings money home. Here, the speaker wants to stress that he is the only one to work, so he says that HE is working, not other people in the home where he's living. Anyway, if you start an email writing "Oggi io sono tanto felice" it's not really wrong, to italian people it may just appear too formal or useless to use the pronom "io" in that kind of context.