It might be tempting to jump straight into an hour-long meditation session, but remember that meditation is like running: you won't run a marathon if you've never trained for it. You'll only end up frustrated.
Treat yourself like you would treat a toddler who's just learning to walk. You'd praise them for making each tiny, wobbly step. And when they trip over their own feet, you'd gently help them get back up and give them lots of hugs, right?
When meditating, reward yourself for the tiniest bit of progress, and don't be hard on yourself if your session doesn't go as expected. If you're just starting, even one minute of relaxed focus might be a challenge. That's OK. Try to meditate for three to five minutes the next time.