How can I solve my problems if I'm not totally immersed in the future, thinking about all the possibilities?
In a sense, the answer is because being immersed in the future is a large part of the problem.
Buddhism doesn't recognize the things you call problems as real problems. They are conventional problems that only obtain the designation because of your own views and beliefs; in reality, whether you solve them or not is mostly meaningless.
This is because Buddhism recognizes the impermanence of life, the inevitability of death, and the cyclic nature of the universe.
286. “Here shall I live during the rains, here in winter
and summer” – thus thinks the fool. He does not
realize the danger (that death might intervene).
287. As a great flood carries away a sleeping village,
so death seizes and carries away the man with a
clinging mind, doting on his children and cattle.
-- Dhp (Buddharakkhita, trans)
Buddhism doesn't advocate the acceptance of impermanence, so much as the realization that it is the truth; once you realize it for yourself, you will give up attachment to the future and the past, since you will understand that their importance is merely circumstantial.
A good advice is to accept that reality inevitably boils down to the six senses - seeing, hearing, smelling, tasting, feeling, and thinking. No matter what comes in the future, good or bad, it will only be some combination of these six categories of experience. This is how one settles ones concern about the future and the past. Even if you are homeless, living or dying on the street, it will only be an experience, not categorically different from living in a mansion.
The closer you come to realizing this, the better, not worse, your life will become (according to Buddhism).