So if you're watching this, I imagine you've already begun to experience changes in your arousal response. Maybe it's difficulty obtaining your erection, maybe it's difficulty maintaining one. The part that I want you to get is, there are many causes that can contribute to what is impacting the quality of your arousal, but it's also true, regardless of that cause, treatment options are available.
So just to give you some background, for many men when you're young and have no medical illness, you're not on any medication, what typically that looks like is, you've begun to notice problems perhaps, with a new partner, or generally and globally, with any sexual partner, problems obtaining or maintaining an erection. Typically, however, there's no difficulty on your own with self-stimulation, and you're often, although maybe not as frequently, still waking with morning erections. That would fall under what we would call psychological factors, and often has a lot to do with performance anxiety or really wanting please your partner.
If, however, you're older and have any kind of medical illness, it could be cardiovascular disease, it could be diabetes, it could be hypertension, and even the medications that go along with treating those conditions, you may then fall under what we consider, either the vascular, the endocrine, or the neurological. These are also reasons that some men are having difficulty obtaining erections.
The first and foremost, I would have you go to your urologist to be evaluated, because they have tests, both in terms of blood work or Rigiscan, which would ultimately let them define what is, for you personally, contributing to your difficulty. The part I want you to get is, treatment is available. So don't panic. I can assure that will not help your situation, and realize that there's treatment available.