BM, You're comparing yourself to top Women athletes. I'll assume you're male. If you were a female that plays once a week, and has had no formal training Would you serve as well as either of those two players?
Talk to any expert on sports biomechanics and they will tell you the typical female physique is much less suited for hitting powerful serves than the typical male physique.
Also ask a doctor how physically debilitating periods can be for many women. [/i]