Not hopeful #Idioms
• a road to nowhere: not helpful, no chance of success
• be in a funk: be unhappy and without hope
• be on a hiding to nothing: doing things that is hopeless
• lose heart: be discourage
• merchant of doom/gloom: someone who is always saying bad things are going to happen
• not give much for someone's chances: to not believe someone will succeed
• the glass is half empty: pessimistic on something

Youth #Idioms
• in the flower of someone's youth: young and the most active period of life
• at your mother's knee: learned when young
• knee-high to a grasshopper [informal]/spring chicken: very small, young

invalid #Vocabulary
/ˈɪnvəlɪd/ noun: disabled/weak person
• He is invalid as he faced a tragic accident.

/ˈɪnvəlɪd/ verb: remove (someone) due to injury; disable by injury
• He was invalided out from the military because his leg was shot by a gun.
• He got invalided due to breaking his bones.

/ɪnˈvalɪd/ adjective: false
• Without providing any solid proof, your argument will be counted as invalid.

Word forms:
• invalidly (adverb): in the false way