Talking yourself out of hard things and challenges is the surest way to know that you won't accomplish the thing you're backing down for. Not doing it won't get you anywhere. The thing about challenges and walking away from them is that it sets you back and slows you down. Never will trying put you back. Even if you don't accomplish it, you get some experience and your next try may be successful.
Honestly, for me, sometimes I'm just lazy. Thinking about getting some of these things done, it's like WHO DONT HAVE TIME FOR THAT IS ME! However, I can absolutely make time if it's something productive and fruitful. You do have to have some discernment about what you actually want in your life and only go for challenges that serve your goals.
If you're presented with a challenge and you think, I absolutely "CAN'T" do this. Think about why you feel like you can't do it. Think about whether it will help you if you do complete it. If it is something that will help your progress, commit to trying. Even if you don't complete the initial challenge fully or in the correct time, know that what you did is progress!