They believe right..
You must believe in yourself and be a stubborn Sonofa to really last in soase multiplayer.
You must lose your ego with your early losses, to be regained later with your constant theoretical victories.
Having ego after say 10 games(and losing most) is a sign that your skill and your perception of your skill don't equal.
Try to get them to equal, and realistically set goals to "beat player X", or "learn strategy X".
Study replays to give yourself fast game experience with the added plus of fast forward.
Learn how to use time wisely.
And most of all new players, LEARN HOW TO COUNTER A RUSH!
Its easy, build fleet, then if they attack you, defend your HW with turrets/repairs while still building fleet.
You can do this and win with a standard economy.
While you do it, you must ensure that your opponent isn't getting a better economy.
And that, isn't always easy.