Jesus promised the disciples that although they would face great sorrow upon separation from Jesus, said sorrow is temporary, and the disciples will get everlasting joy. In fact, in the day where the disciples get everlasting joy, Jesus told them that "[they] will ask [Jesus] nothing." (16:23) Jesus and His provision of everlasting joy provides perfect counters to uneasy feelings, so the disciples have no need to ask Jesus anything (especially the doubts).
Additionally, Jesus reiterated the promise on how if the disciples "ask the Father in [Jesus's] name", the Father "will give [them]" (16:23). It's worth noting that "asking in Jesus's name" means "asking in Jesus's character/reputation", which is supported in the definition of the Greek word for "name" (Strong 3686). However, the disciples haven't yet asked in Jesus's name, so Jesus calls the disciples to ask so they can receive, "that [their] joy may be full" (16:24). The disciples can receive since Jesus is the mediator, and Jesus also promised everlasting joy.