Always stretch and flex before engaging in lifting, and don't carry on for too long. Strained muscles can pull oddly and unexpectedly, resulting in injury for seemingly no reason.
Jeff from Athlean X would like a word with you
@MisterXiado
Stretching is KILLING Your Gains!
https://www.youtube.com/watch?v=nLQefKzMVjo
tl;dr of what you should be doing:
[ul][/ul]You shouldn't hold a static stretch for long before you do any lifting (i.g. over-extended stretching or 30second stretching).
[ul][/ul]Dynamic stretching is fine.
[ul][/ul]Static stretching is best during muscle recovery or post-workout, not right before you lift.
[ul][/ul]Stretching regularly at night/morning/post-workout makes sure you don't have strained muscles and promotes muscle length.
[ul][/ul]It is a good idea to go through the motion with a small amount of weight before going for anything larger.
[ul][/ul]You're more prone to injury if you stretch heavily before lifting.
[ul][/ul]Proper form is key! Without good form, you're just asking for injury and longterm muscle/joint problems. In this case lift with your legs and put the pressure on your heels. Don't lift with your back!