I worked out yesterday and my legs still feel really tired is it because i worked myself too hard?

Tired after exercise: You are likely just de-conditioned. Whether it's strength training exercises or aerobic exercises you are referring to, both can caused delayed onset muscle soreness or just general tiredness. Allow your body time to adapt and rest in between. Most importantly, refrain from exercising while you have any kind of infection or fever. Your immune system needs all the precious calories for healing.