Sacrificing present happiness for the future is the definition of a long term goal. Today I sacrificed alcohol I would have enjoyed so as to continue losing weight. If I thought I wouldn't be alive months from now to experience the benefits from said weight loss, why do it? Ironically that attitude would actually increase the odds of early-onset nastiness.

Why put money into my 401k that I can't touch without penalty for 40 years when I could enjoy it now?

Being content and at peace with oneself in the moment is possible, and should be striven for. But for my part I'd have a hard time being content with myself if I wasn't striving for better for both myself and my family.

In my experience the only lasting satisfaction in life comes from discharging meaningful responsibilities, that requires some sacrifice of momentary happiness. Happiness is great when it's around but has no staying power, and too many people get sucked into miserable hedonism while trying to turn it into a constant.