The training of ourselves should be done before the age of puberty starts. But it is never late, Allah (SWT) has placed all types kinds of feelings, in our body in order for us to pass this life without us being bored.
Allah has placed these systems, and it should not be abused.
When the soul comes in the mother's womb, and stays in the body during the lifetime until death, it is just like one would rent a car, and if you rent a car, and be involved in a accident, any damage done to the car has to be answered. If one is driving a car, for example, you cannot let go of the car without controlling the starring, otherwise the car will hit right or left.
The same way Allah (SWT) wants us to enjoy the right of our body in this world, with all of the attractions, within the guidelines of Islam, so we do not abuse our body, or damage it because, this body belongs to Allah who is the creator and provider, and the soul travels from birth to death.
Now the soul which controls the body, for example if one sees pornography, or easy money available to steal, or any other attraction of this world, such as girls, wine, ect. When we involve in things like this, by just looking it feels like we are involved in this, and enjoying the taste of all of those actions. And our desires, then Satan sits on our desires, and tells us to go ahead, what are you waiting for, who is watching you are you not a modern person, are you backward, or what will people think about you, where are you coming from, all kinds of doubts like this are placed by Satan.
And if you that time involve in those actions, and do not control yourself, then you are breaking the laws of Allah, and you are unable to keep yourself in the boundaries of Islam. And the person who does not involve, he will still get mercy for not involving in these types of major sins, so one would get a warning in his heart, one would say to himself to stop, what are you doing? Whoever at that time stops, and controls his desires, is a winner. And who is unable to stop, then he puts himself towards hell.
Allah will not come to us and tell us to behave ourselves, this is like a test, or writing an exam.
When we write an exam, we can leave a blank paper, or we could write the best, or do everything wrong, the examiner will never come and question us, what are you doing, why are you making it wrong. We all wait for our results.
This worldly exam, if one fails, can rewrite it. Or can change your line, you will not be hanged for it.
But if your soul fails the exam of this world from Allah (SWT), then there is no way to write this exam again, because there is not way to come back to this world after death. And there are not telephone lines in the grave yard, to complain and ask help from one's friend or relative. There will be no shelter or medical facilities, is it worth it to go after our desires? Which will lead us towards hell forever.
And by Nafs (Adam or a person or a soul, etc.), and Him Who
perfected him in proportion; (91:7)
Then He showed him what is wrong for him and what is right for him; (91:8)
Indeed he succeeds who purifies his own self (i.e. obeys and performs all
that Allāh ordered, by following the true Faith of Islāmic Monotheism
and by doing righteous good deeds). (91:9)
And indeed he fails who corrupts his own self (i.e. disobeys what Allāh
has ordered by rejecting the true Faith of Islāmic Monotheism or by
following polytheism, etc. or by doing every kind of evil wicked deeds).
(91:10)
The best way to control one's desires is to maintain five times prayer on time, and to ourselves in wudu (ablution). Because when we have no wudu (ablution) and are not cleaned, then Satan takes place in our body. Wudu and Prayers is like a shield of our body, in order to protect ourselves from evil desires.
As soon as we are involved in this world, evil desires take place. And we start to melt just like an ice cube placed out of the freezer, towards this world. So if we melt over here, what will be there for us to take when we complete our test from this world.
(It will be said to the pious): "O (you) the one in (complete) rest
and satisfaction! (89:27)
"Come back to your Lord, Well-pleased (yourself) and well-pleasing
unto Him! (89:28)
"Enter you, then, among My honored slaves, (89:29)
"And enter you My Paradise!" (89:30)
Allah is mentioning in the verse above, to us that it is not worth it for us to go after this world, we should relax and focus on Allah. And not to follow the footsteps of Satan, whatever has been done, Allah will forgive inshallah, but we should go to the right path, where we are suppose to be. And if we are on the right path, Allah will be happy with us, and we will be rewarded here and in hereafter, and we will be counted as pious people, inshallah.