Delayed Onset Muscle Soreness is a painful condition. Normal muscle soreness results immediately after doing an exercise and usually lasts for less than two days. Doms only occurs when your body is not fully developed to handle heavy and intense workouts which results in structural damage to muscle tissue and tendons that can last for days. Anti-inflammatory drugs can help recover (over-the-counter pain killers can slow muscle growth and damage your liver). So if you feel sore for more 2 or 3 days then you had way too much, scale down on the volume of your training but don't stay away from the gym. Do light training to help recover faster.