A change in your social life is inevitable. But, the startup stages can be especially isolating because you may feel as if you're "cheating" on your business by going out and having fun. That is exactly how I felt.
I let this isolation go on for almost two years. And then, I decided to optimize my schedule in order to be more effective for both my business and my mental health.
I find it best to get up very early (think 4:00am to 5:30am) and get to work. This way, I can hopefully cross off every item on my to-do list between noon and 3:00pm.
I'll admit, there are many days that I don't implement this strategy.And on those days, I usually find myself glued to the computer well into the night. It's still a work in progress, but I can personally vouch for the effectiveness of this strategy.