Getting the girl of your dreams in your bed? Amazing. Failing to get an erection when you're ready to go? There's absolutely nothing worse.

But before you freak out, know that lots of guys can have trouble getting hard when they want to have sex, and it doesn't necessarily signal that you have erectile dysfunction. While it's common in older guys, lots of younger guys can have issues getting and maintaining their boner, too.

A lot of that can come down to psychological or environmental reasons, explains Jamin Brahmbhatt, M.D., a urologist at Orlando Health. So here are five innocent reasons that might explain your inability to perform. Keep them in mind next time sex doesn't go the way you planned.

You can’t get an erection because you drank too much alcohol

You’ve probably been in this situation: You’ve had one too many drinks, take her back to your place, and realize you just can’t get hard. Thank whiskey dick, one of the most unfortunate curses to fall on mankind.

Alcohol is a depressant on your central nervous system, says Dr. Brahmbhatt. It decreases blood flow to your penis, which can prevent you from getting hard.

So while that drink might relax you enough to get her into bed—and it’s true, some guys might perform better with a tiny bit of booze in their system—it might prevent you from getting the job done if you go overboard, he says.

So be conscious of your limitations: Guys should stick to roughly two drinks per day, according to the Centers for Disease Control and Prevention. While everyone’s tolerance is different, it’s a good benchmark to keep in mind if you plan on doing the deed once you get back home.

You can’t get an erection because you’re with someone new

You finally get her to come home with you, but as soon as you try to have sex, your member wilts—along with your confidence.

That can come down to lots of things. For one, it can be completely psychological, says Dr. Brahmbhatt. So if you’re insecure—say, you feel like your penis size might not stack up to other men—or if you’ve had super awkward sexual experiences in the past, your brain might not be able to let go of that when it comes time to perform.

Plus, your body might physically experience this as a high-stress situation, and pump your system with adrenaline, killing your ability to get it up, he says. (Want to maintain your erection for life? 

You can’t get an erection because you’re stressed and exhausted

When you’ve had one too many meetings, your boss won't give you a break, and you’re on the edge of burnout, sex can be the last thing on your mind, says Dr. Brahmbhatt.

“Stress exhausts you mentally and physically,” he says. “When you’re stressed out, your body is trying to mobilize all of your energy to your main functional organs, so something like your penis is going to be the last thing on this list.”

What’s more, feeling stressed can spike your cortisol levels. That can be a problem, since the stress-hormone can actually block the effects of testosterone, a study published in Hormones and Behavior found. That can kill your libido and cause problems with your erections. 

The good news is, alleviating whatever is causing you to tense up can usually squash these issues. And once you feel less burnt out, having more sex can keep that stress-free momentum going, says Dr. Brahmbhatt.

You can’t get an erection because you’re taking certain medications

There’s a whole slew of medications that can interfere with your ability to get hard, according to the University of Maryland Medical Center.

That includes certain high blood pressure medications, like beta-blockers and diuretics, says Steven Lamm, M.D., medical director of NYU Langone’s Preston Robert Tisch Center for Men’s Health. While they’re great for your heart, their interference with your sympathetic nervous system and blood vessel walls can decrease the blood flow to your rod.

Standford University research suggests that up to 75 percent of depressed patients see a dip in their libido. And taking certain antidepressants to treat that depression can tank your boner, too. Serotonin reuptake inhibitors, like Prozac and Lexapro, can decrease your testosterone levels or even lead to delayed ejaculation.

But you can’t just stop taking those medications if you’re dependent on them. If you think they’re screwing with your sex life, you can talk to your doctor about other options. In many cases, they can work with you to find a medication with a lower dose or different class to minimize the boner-killing side effects, says Dr. Brahmbhatt.

You can’t get an erection because you recently masturbated

If you just got off solo, you might have to wait before you can hop into bed with your partner, says Dr. Brahmbhatt. It might have something to do with a spike in the hormone prolactin after you orgasm, according to a study published in the International Journal of Impotence Research. This hormone has been linked to difficulties maintaining an erection or even ejaculating.

Scientists aren’t sure why your refractory time varies, according to the International Society for Sexual Medicine, but it’s often shorter for younger men.

“It’s like running a marathon, your body will need to relax and rejuvenate before your run again,” explains Dr. Brahmbhatt. So just keep in mind that the average man has a 30-minute refractory period, he says, but some guys may need as little as 10 minutes or up to an hour or two to reload.