A man's penis gets hard because blood is pumped into it, like balloon

There are several basic reason why your penis doesn't get hard enough any more. The causes are both emotional and physical.
To simplefy things, you can say it's either because it's not enough blood flows into the penis (pumping in) or too much blood leaks out of the penis (leaking).
I don't want to go into any technical details. The main thing is that if your cause is physical, then you must exercise all the muscles around the genital area and balance the energy flow down there. (including the soft muscles in the penis itself that prevent blod from leaking out).
If the problem is emotional (usually connected to anxiety or stress), then you need to learn relaxation techniques and a few basic 'emotional techniques' that will bring you back to your old self. You'll be amazed what these techniques will do to your day to day life too.
Most men benefit most from practising both the physical and emotional techniques. That was what I tought Sam and that's what I want to teach you too.