Our most sacred fluid our semen is not to waste and that's no different in a relationship and sex. If one doesn't have a partner then its smartest to do Semen Retention ofcourse. However, in a relationship I think you can have what I'll call Partner Share Retention. This is to have sex but not to waste the semen. No condoms to pollute your Semen with plastic (and limiting the pleasure), no pills and such that goes without saying, either pull out method or no vaginal penetration which btw is also very fun and takes a longer time!
We know Semen is full of nutrients so if the force of love dominates to make love with your partner then it's either for vaginal intercourse and procreation, Or .. Semen absorption by her. Semen absorption without penetration (unless pullout method) is like a sacrifice you do to her gifting her rich nutrients from a manly body and the masculine energy world. She can either absorb your Semen by skin (i guess better in the night where you sleep after action so it has time to absorb) or simply swallow it. If your partner is not comfortable swallowing then either you have a poor diet and health thus making it taste bad (animal based foods and non processed is the healthiest), or she is too afraid and unwild, or maybe not submissive enough altho anyway make sure it is healthy and tasty. And don't be shy to try your own abit with her. theres no issues with it and in fact women find that hot and would also be encouraged to swallow if you're eager do it yourself.
So this way you have both the fun with love, and those sacred nutrients will be used and gifted to her. Imagine how much health this can bring to her in her pregnancy. And imagine if this somehow becomes tradition, how well we can manage the world population without the need of condoms and all that plastic chemical stuff.
Edit: PS ofc there's the pregnancy chance with precum if no condoms used I forgot to address this, however there are a couple of days in the woman's period were she can't get pregnant. So maybe we are not meant to be having penetration sex the whole time in her month, but in some days of it. Seems also good to abstain for 3 weeks and come to action with full energy.