I used to lift weights 6 days a week when I first started weight lifting. Years later, I backed it down to 4 days a week.
In weight lifting, you can injure yourself in three ways, 1. bad form, 2. lifting more than your body can handle, and 3. not being warmed up enough.
If you lift more than you can handle but you have a spotter to help you or you put the barbell down on power rack spotter bars or drop the barbell (if you are doing a deadlift), then you can prevent injury. This is more a matter of knowing your limits and if you know you are near your max, then use a spotter and/or utilize a squat rack or power rack for squats.
Also, don't goof off in the gym. You can injure yourself via horseplay or injure someone else. I see teens goofing off in the gym. Two words: f***boy. It's like this is a gym. Some people are lifting large amounts of weight that could result in serious injury. Don't goof off. I saw this one guy push this bigger guy, just playing around. The big dude got pushed back and hit his knee on a dumbbell rack. I saw him a couple weeks later in the gym with his knee in a brace. He got seriously injured from a friend goofing off.
4. If you need a spotter, ask for someone who knows like what the heck they are doing. I've seen stupid stuff. This guy wasn't that strong but he was struggling near the final rep with like 85 lbs. on a barbell bench press. So his spotter friend starts assisting, but only lifting up the side that is lower. He finally lifts the bar up back onto the rack.
Years later, I ask this stranger for a spot. My right shoulder was a bit weaker, and I was struggling with this bench press, I don't remember how much, but this dude does the same thing I saw years ago. He started lifting up on the one end of the barbell that was lower. What this does is leverage more weight on the opposing chest muscle. So now, I can't lift the side that is higher any farther. He's assisting the side that is lower and using my hand that is higher like the pivot point of a lever, thus increasing the amount of weight that is on that hand. I never asked that retard for help again. Always lift the barbell equally from both sides when spotting on bench press, incline bench, military press, decline bench.
That pump though 
