-----------------------------------
つらい， 辛い
1. painful, bitter, heart-breaking, difficult (emotionally)
2. tough, difficult, hard (usu. of situations)
3. cruel, harsh, cold
难，困难；痛苦、苦涩、令人心碎、难过；冷，严峻
-----------------------------------
日々， 日日， ひび， にちにち
1. daily, everyday
2. days (e.g. of one's youth)
3. every day, day after day, day by day, from day to day
天天，每天；日子；一天天，每一天
-----------------------------------
続く， つづく
1. to continue, to last, to go on
2. to continue (without a break), to be unbroken
3. to occur again and again
4. to lead to, to connect to, to adjoin
5. to come after, to follow, to succeed, to rank next to
6. to hold out, to keep, to last
继续，延续；持续不断地（不间断地）；一再发生；接踵而至，紧随其后，继而，紧挨着；坚持，保持，持续