> I have enough savings to survive for five years.
That's three to four years more than most people who make the jump.
If you're already making money from your side project, again, you're ahead of most people who make the jump.
Sounds like you should go for it!
The biggest thing to watch out for is getting lonely. When I went off on my own, I had a wife and kids. So I get to see them every day. If you work alone, you may not have any human interaction for a day or two, or longer. Human interaction is important to maintaining sanity. So make sure to make up for it somehow. Go to meetups, join a social club, be proactive about meeting up with friends, something to get you out of the house and interacting with other humans daily. Even if you're in an introvert, you still need human interaction. Find something that works for you.
> To not stick to a schedule/routine once I am solo
A lot of people have that fear, and it's pretty easy to solve. One trick involves starting every day with a walk around the block and ending each "work day" with another walk around the block in the opposite direction. This is your "commute" and puts you in the right mindset. You can do something else if you don't like walking, like make sure you start with a workout or a shower.
> People's and family opinion.
That's a hard one. Every family and culture is different. But in this case profitability solves a lot of problems. If you can respond to the naysayers with "I'm making money not losing" then that's a good way to appease most criticism.
> Failing and losing motivation.
Another hard one, especially if you have a lot of savings. You need someone to hold you accountable, either a cofounder or even an employee. Or depending on your relationship, maybe your girlfriend. As her to check in with you specifically about the business every week. Or if not her, another solo founder somewhere.