Your experience of magic and casting on the battlefield has allowed you to vastly improve your magical capabilities when in combat 

• You have advantage on Constitution saving throws that you make to maintain your concentration on a spell when you take damage.

• When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and can't target multiple creatures at once 
• You can perform the somatic components of spells even when you have weapons or a shield in one or both hands as you are now highly proficient with this