When someone has bitten off too much, it generally means they have taken on more than they can handle. The antonyms for this phrase would be to take things in moderation or to not take on too much. By taking things in moderation, one can ensure that they do not become overwhelmed or stressed, and are more likely to achieve their goals. Similarly, by not taking on too much, one can avoid burnout and maintain a balance between work and rest. Overall, it is important to remember that it is better to do less and do it well, rather than trying to do too much and falling short.