Samaras is out of contract at the end of the season and has been offered the chance to stay with the Scottish champions.
However, Spanish title challengers Atletico Madrid have been linked with a move for the Greece international, who is currently weighing up his future.
Mjallby left Celtic for Levante during his own playing career and believes it will be difficult for Samaras if the 28-year-old joins a club not in contention for success.
"It was strange to leave a massive club like Celtic where the demands are so high," said Mjallby in the Sunday Mail.
"I loved that situation but then I signed for a club that was much smaller and without the same facilities or people looking after you. It was a wake-up call. It was a new culture, which you must accept, but in a way I regretted it.
"It could be difficult for Sami if he signs for a club which isn't competing for titles. He loves it at Celtic where he fights for trophies. It's what football is all about.
"He is well off financially anyway. When he finishes he can look at the prize cabinet and bank account.
"Sami is a laid-back guy but he's clever too. I hope that if he does leave Celtic he signs for someone where he has the chance to win trophies. You'd hope it was a club fighting for the title rather than fighting off relegation.
"Georgios has a great reputation in Europe and I'm not surprised a lot of clubs outside the UK are interested in him.
"He has been one of our best players in the last two years. He has been great in Europe while also playing very well for Greece.
"This is an important time for him. It might be his last big contract, or long-term deal anyway. He's back home in Greece and will give an answer soon."