adults have got to take children seriously, listen to them, make them feel that they are important, encourage children to try things out for themselves (you start with young children, by being close by, so they know there is an adult there if they need them - this often gives them more confidence to try things). You praise and encourage and praise, if they say things such 'I can't do it, or it's wrong again' when completing a jigsaw, you encourage them by saying they aren't doing anything wrong they are trying/practising; you can tell them when you learnt knitting/cooking/skiing you had to try many times until you could do something.
You help build children's confidence, self-esteem and self-image - having those will help anyone (of whatever age) and build up resilience to try things out, not give in or up, learn that it's perfectly normal to try some things often before they have accomplished something, but not worrying if they don't succeed in everything.
You can help by talking at circle time of something that you are not so good at i.e. every time I try and grow a plant it dies, and finish off with - but I'm very good at washing my car and making it shine like new. Read stories of resilience i.e. Jack and the beanstalk. Resilience is something that needs to be built up in layers. Some children may have a better disposition/character that may make them gain resilience a little easier, for those that don't have such an 'easy' nature, they may need a little more help to gain skills to help them build up their resilience.