I know that sometimes strength and endurance exercises might seem as most important part of your workout.
BUT please don't forget about stretching!!!
There is no such thing as unanimously made statement that stretching before exercising is obligatory, but it will not harm you if together with warm up you include some stretches! What has been proven is that stretching is seriously important after exercising!
It helps your muscles to keep their natural and normal length! It's not going to decrease your muscle strength results, it's not about who can make split or who can put his leg over head, it's about your general health and wellbeing. Flexibility is one characteristic of muscle along with endurance and strength.
Your muscle should be strong enough to do the movement and also long (flexible) enough to cross joints and allow your body full range of movements.
So, if you avoid stretching, with time you can start to have complains about pain in joints(knee joint is one of most popular area), develop muscle imbalance - again pain and changes in posture, with years reduced range in movement means that your non contractile structures will lose elasticity and you can more likely get yourself in unwanted trauma. I'm not even going to start about arthritis, Osgood Schlater disease, "growing pain" in young sportsmen etc!
I have spent at least 5 years repeating at least twice a week - don't twitch it, don't rock or swing that movement, don't pull it using strength, you don't have to feel pain, just moderate stretch etc.! And nothing have changed! When you do your stretches - take your time, do them at home if you don't feel like staying at gym that long, but you have to take your time!
So each stretching position you have to start really easy- mild sense of stretch, hold it there at least 10-15 seconds and then gently try to go farther and again 10-15 seconds, if you can go even farther after that - good, if not stay there another 15 seconds. In total it should take around 1 min for each position.
If you suffer from pain in any of your joints, ask yourself - do you spend enough time for your flexibility training?!