לרפואת נעמי בת טובה בתוך שח"י
There is a fascinating Tosfos in Sanhedrin!
Tosfos [59b] says that the mitzva of having children has a passive element to it. How so? The prohibition against spilling seed is the other side of the coin. One side is "have children" while the other is "guard your seed".
So what does this mean practically? That when one marries and is involved in the holy mitzva of procreation he should have in mind that he wants to fix the earlier sin of wasting his seed. This is in line with the rule that the tikkun of a לאו that is derived from an עשה [as the aveirah of wasting seed derives from the עשה of having children] is by fulfilling the עשה.
Moreover, Chazal say that with the limbs with which one performed bundles of aveiros he should perform bundles of mitzvos. So when one is married he has the opportunity to fix the past and do bundles of mitzvos.
This DOESN'T mean that one should be with one's wife a lot. The gemara already said [Brachos 22] that this should be avoided and one must control his urges. It does mean that when one is involved in the act it should be done with holiness and purity.
In the words of the Master: