Here is the thing...we all have the quandary early in in our progression as a player of how long do I stay? If you win a fight, and are able to claim an objective, the correct answer is leave now. Not push for one more. Rarely is pushing for more than you can take uncontested a good idea. Opportunity will come again for that next tower. Don't give the enemy a chance to come back to lane with better items and health and numbers and wipe your team. They will! Almost every time. Good players figure this out and take what they can get, back off, die less and win more games. Bad players always bite off More than they can chew, win early, die a lot over commiting later, and wonder why their teams always throw games late. You let a hungery team hang around till the end and make questionable decisions over and over and you will lose more often than not.
Take it from someone who has been there. Back the heck off and pick your moments wisely. Keep your eyes on the map and always consider the enemy is ganking whoever is extended if you can't see them on the map...9 times out of 10 that's exactly what happens.