training to failure every workout you do , is surely going to take its toll and eventually leave the body exhausted I assume we are talking to failure on every single exercise.,in one gym session and on every single set .When you sit down and think what that really means in terms of your own workout, if thats what you want to do -train to failure, then it would be wise to ensure other factors are in place , such as adequate rest /sleep,proper nutrition and elimination of outside factors such as stress from work, partner and financial worries.Personally i dont think push to failure is necessary , as long as the muscle is continually under tension during each rep , it will respond,This could mean lighter weights , more reps but keeping up the tension especially on negative reps rather than let gravity take hold -just my view