Get some training!!! Did you attend any firearms training class that included low-light conditions? Did you attend any firearms training class?
You should carry a handheld flashlight anyway. You may never actually need to use your handgun to defend your life, but you will certainly need to use your flashlight at some point in your life. I know I have. Learn how to use a handheld flashlight with a handgun in a quality training class and not from Internet gun forums. There is
a lot to learn. Once you have done that, you can still decide if you need a weapon-mounted light in addition.
Watch this
series of low-light videos:
I do not have a weapon-mounted light on my Glock 19 at this point. I did for a while. For me, it just complicated things without much benefit. I did broke the battery door of my TLR-1 twice within two years. I am assuming this was due to impact and stress on material while the light was mounted.
PS: Don't go overboard with lumens. I have a
Streamlight ProTac HL primarily becase it can also be used as a blunt instrument and to temporarily blind people. It has 35/750 lumens. I programmed it to go to 35 on one click and to 750 on two. It is easy to blind yourself with a high-lumens flashlight while inside. I see enough with 35 lumens to make decisions.