The life humans have is about progressing. We may be progressing into disaster but it's still us moving forward, staying put is not going to find any form of satisfaction. Life is changing anyway, and we are changing every day even if our lives seen banal and ordinary. Just by getting up every day, eating and drinking to survive we are moving forward.
Therefore, even if you don't find the cure for cancer or become a president, everything you do has an impact somewhere even in ordinary lives. But something you did or said at one time may have stuck with someone and changed their thinking/life, if you decorate your home, if you improve your garden, if you work every day, if you have a child, if you buy goods so the provider can then look after his family....you are making an impact, changing the world in minute ways..
Feeding the birds, caring for a dog/cat, planting a tree, cooking a meal for a friend, looking after yourself with a walk/bike ride/swim/gym session/dance...all give satisfaction and an appreciation for nature, others, life. It may not make you 'happy' but surely a degree of contentment and a feeling of being alive/of use.
Therefore contentment is in the small things, not necessarily the cruises, expensive shoes, flash cars etc...all of which help but are fleeting and not of the every day.
If comparison of others deflates you, then compare with those who are very sick, starving, homeless, cold, brutalised, terrified, with no where to turn and with no one .
I also think motivation has a part to play here. I'm motivated...to make the most of every day, find something to do, somewhere to go, move, have ideas etc, even if it's just enjoying reading a book. I know someone who sadly isn't, it's maybe not her fault it could be genes inherited [it's not her past, mine has been dire at times, really]...but she moans and never changes anything despite being more than capable of doing so and having the funds. It's constant, and the years go on......I think motivation and the satisfaction that it brings is also about one's attitude. And we can work at changing those.
I started life as a happy baby, a happy child [ok so I was maybe lucky, but the circumstances were pretty awful at the time, of course i didn't know that, I was shielded from it]...and that is my start off point. Since then I have been very unhappy at times, for long periods. I've had to do a lot of work on myself. I now get rid of what does not suit who I am, I do not do things I don't want to, that make me unhappy, I do not see people who have hurt me badly. I clear it all out if and when it happens. I'm now left with myself, live alone and I am content. It's how I felt as a child, before the world kicked in and said I had to do and say and go where I wasn't comfortable. Chasing happiness doesn't work. Just be who you really are and enjoy what you need to do. We are lucky to have a chance to change our lives every day.