If you've caught yourself spending too much time in the past or the future, read the 4th Pathway of Ken Keyes: "I always remember I have everything I need to enjoy my here and now unless I am letting my consciousness be dominated by demands and expectations based on the dead past or the imagined future." Remind yourself you have food, clothing, shelter, mobility, vision, hearing and basic necessities. Many people don't.
You needn't try to convince yourself that everything in your life is fine; just know that right here and right now, if you aren't stuck in "how awful it is," you can calm yourself and change your negative thoughts to accepting what is so now. That doesn't mean you won't do anything about your situation; it just means that what you are and have right now can be dealt with, minus panic and fear.
Do as Burkeman suggests in The Antidote: Happiness for Those Who Can't Stand Positive Thinking. He believes people work too hard on some goals. For him, life is about being comfortable with uncertainty. What may support you in that awareness is to pull up some examples from your and others' lives of when you made it through tough times. It could relate to financial, romantic, career, or other situations. For me, when I added a very large amount to what I'd owe on my mortgage for a real estate investment in 2008 which lost money, I remember my fears about possibly losing my own home. I remind myself even now when financial concerns come up that I made it through that difficulty. I do have a larger mortgage payment now, and am able to pay that with rent from my six housemates. I see no value in spending time thinking about what bad things could happen. I don't mean to ignore what's going on. I do mean to remember that, right now, you are probably managing the best you can, and you can't expect more than that, from yourself or from others.
Find at least one or more ways each day to treat yourself. That could mean anything from reminiscing over favorite photos, to enjoying a dish of ice cream, to sitting in a park daydreaming, to watching TV or swimming or dancing. If you make a list of favorite activities and feel stuck on a particular day, pull out that list and pick one that feels good to do, now. If it serves you to complete one or more tasks before your treat, that works too. Just know that, right now, you are doing the best you know how to meet your needs. I believe that self-care, self-love and treats are good for all of us.