If you absolutely must LTR then i'd like to suggest some guidelines to minimize potential damages. They are good rules of thumb for most men but especially young men.

1. Never become emotionally dependent on "your" woman. If your heart is a basket of apples, she can have a few but certainly not most or even half. Keep the connections with your friends and family. You dont want to be an emotional wreck w/o support when shit hits the fan.

2. Stay focused on your goals. Career, finances and the like. "Your" girl should be a benefit or at least not in the way of your goals. Get fit/stay fit. Save/invest money. Take her out and be nice but remember shes expendable. Your resources and yourself are not.

3. Realize that things change and things end in life. Your LTR is no different. Enjoy it while it last but get that forever thought out of your head immediately.

4. Do not become financially dependent on "your" woman. Ive seen guys do this and it works for a while but she can and most likely will drop you at a moments notice, leaving you broke and homeless. If possible, keep your own apt/house even if you are crashing at her place frequently.

5. Frequently imagine her sucking another mans dick. I know it sounds brutal but its good way to obliterate the idea that shes "yours". Obviously you dont want her cheating on you but if she does.... no surprise. Its happened since the beginning of time. It'll be much easier to cut her off if you keep this in the back of your mind. Shes sucked dick before you, she will suck dick after you. Just enjoy while shes on yours.

6. Explore with her as much you can sexually and demand proper treatment early. Do not be afraid to ask about kinks, asking her to do your laundry ect. During the honeymoon stage, film sex sessions and upload them to email/cloud/ hard drive. Women care about their reputation alot. She'll automatically think twice about disparging you if things end badly. Also, its a good way to plant your flag like a dog pissing on tree and shifts power in your favor. But dont be malicious. Possible jail time can result.

7. After 12-18 months in, you should really be thinking hard if this woman is worth more years of your life or if its time to go a different path. The most valuable thing is time. You shouldnt just give that away. Betas do that. You are valuable and so is your time.