Using your toilet handle to flush the toilet is a pretty mindless thing to do until there is an issue. Maybe you notice that it is becoming loose and wiggle a lot when you use it, or maybe you have to get it just right to be able to flush.
The assembly that controls flushing is not very complicated, but your handle is definitely a weak spot.
Tightening or replacing a toilet handle is a simple process, and could possibly be done without any special tools. You should always make sure that you turn off the water supply before you start working on your toilet since there is a danger of water damage if something goes wrong. You should also make sure that you know what the problem is. If you flush once or twice with the lid off of your water tank, you will be able to see where the problem lies.
Sometimes all you need to do is shorten the chain that attaches to the flapper to tighten things up. You should however not make it so short that it leaves your toilet constantly running.