You are proud of "me mate." Who is "me mate?" Were you attempting to state
that you were proud of yourself? If so, then use "myself." If you were attempting
to address me or another user by "mate," do not. I am not your "mate." Use our usernames. When you address someone in writing form, the comma should
separate your audience. Outside of this forum, here is a correction that you can
write to an actual mate: "I am really proud of myself, mate. I started to learn
English three months ago."