Using a lubricant is not about what you can or cannot produce yourself. It is about protection and that is what is most important. It doesn't matter how wet you get, the walls of your vagina are very delicate membranes and fast, repetitive penetration will tear those membranes. The tears are microscopic, but over time, they will affect the elasticity of one of a woman's most prized posessions- her vagina. So, if you want to stay tighter and stronger for longer, you should ALWAYS use a lube for sex whether it is with a partner or with a toy.
If you use condoms (safety first!), make sure that your chosen lubricant is condom safe and that it is the appropriate type for the kind of sexual play that you will be engaging in. Water based lubricants are safe to use alone, with toys and with most condoms. If back door play is in your future, make sure you choose a lubricant that is made for that, like a Silicon based lubricant.
So, get out there and find your lubricant . Your vagina will thank you for it!!!