The best way to lie is to tell the truth with a spin or to tell the truth unconvincingly, for exactly the reason you quoted from Samuel Clemens, always tell the truth so you don't have to remember what you said
Personally I hate lying also for this exact same reason, I don't want to have to remember a falsehood, it's just too hard.
Lying in a relationship, once you know it is there, is very hard to forgive and it is unlikely that the other party will change, if they can lie about one thing they can probably lie about anything.