The way bear spray works, you create a big cloud of spicy air in between you and the bear and the bear runs into that cloud. The bear very quickly decides to go do something else with it's life the second it gets a breath of that air. You don't wait until the bear is close enough to hit directly with with spray, you spray as soon as the bear starts charging or gets too close. It's manual or operations is very different from pepper spray for people.

Just like you should be well-trained when carrying your gun, you should have had the training on how to properly use bear spray. This concern you've voiced suggests you bought a can and assumed you knew how to use it.

Here's a fairly decent video to start with.

https://youtu.be/TZ5HJHZ8Mfw