This way I can easily speculate a bit on buying/selling bitcoins when the price is right.
on first comment you said is correct not to use same password for all accounts , keeping different passwords give you more security to your accounts,
About believing exchanges is how old is the exchange like yobit and kraken they are olddest exchanges who are going good so in this exchanges you can keep you bitcoin safely as they have big business and wont run away with your coins. If the exchanges is new then their is more chances of running away as if they dont get sufficient business income to run the exchange.