What you want is find out how marijuana works before trying it. Essentially, there are two mainly psychoactive chemicals in a cannabis plant: THC and CBD, each one is more prevalent in sativa and indica strains respectively. THC improves concentration, helps in imagining the problem, and is a hallucinogen (think towards LSD from sober). CBD gives you a couch-lock, makes you sleepy and is a sedative (think towards Xanax).

Sativa-dominant strains will have more THC than CBD and thus help you with your problems immediately.

Also beware that THC is a mild psychedelic so all the "set and setting" rules apply.