After a stunning start to the campaign that had them assume pole position in the challenge for promotion, the Jags have faltered in recent weeks as they have fallen five points behind leaders Morton into third place.
With two games in hand over the Ton and fellow challengers Dunfermline, Thistle's promotion destiny is still in their own hands and the Jags boss wants to see a tougher attitude from his players.
He said: "We have got to handle the pressure, it is as simple as that. There are bits that they are doing right, but it is sometimes a bit hectic and frantic.
"We are only coming into half way in the season and we have got to get the bit between our teeth in every game. Every game is different but, as I say to them, the first goal can be crucial in games in this division."
Thistle have not won on First Division duty since a 3-2 win over Raith Rovers in mid-December, dropping points against Morton, Airdrie, Livingston and Dumbarton in recent weeks.
The Jags have put the undersoil heating system on to ensure tomorrow's clash with Falkirk goes ahead and McNamara expects another close encounter against Steven Pressley's side.
He said: "We played them at Falkirk and they played a 4-1-4-1 system at home against us.
"They sat in and tried to catch us on the break and I would be surprised if they came and played differently on Saturday.
"We need to be patient and not go gung-ho. We want to win the match, but it's important that we keep our focus and our discipline, which is key in every game.
"Lyle Taylor has done well for them and scored a few goals.
"In the games I have seen, he has been isolated for a lot of the time, but his goals speak volumes for how well he has done for them."